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Introduction In this series of blogs, I am going to show how to create an on-chain and off-chain NFT collection smart contract and create a DApp to mint NFTs. I am also going to show how to create your own DApp which I designed for fun last year and also to learn about NFTs and DApps. Idea The idea to create an NFT DApp is inspired by the loot project but I also want to add my own flavors of creativity to it and understand the working of smart contracts in the process. Learning Before this, I tried out different things like building my back in July 2021 when I am new to cryptocurrency space and understanding little things like how is used. own token on the Ethereum test network merkle tree It is this time when I learned about , MetaMask wallet, different test networks of Ethereum blockchain, deploying smart contracts through remix IDE. I also learned little things like we can deploy the same contract which deployed on Ethereum blockchain on other blockchains like Binance Smart Chain. remix IDE I have decided what to build but don’t know how. I began exploring some resources with little knowledge and found this from a Reddit post. solidity tutorial I have gone through the solidity basics to understand code from verified smart contracts and to develop new ones. Smart Contract Development After getting a bit of knowledge on solidity, I began exploring the smart contract of the loot project. It didn’t make much sense but after spending some time with it, I understood the working. I know ERC-721 standard is used to build NFTs and ERC-20 standard to build our own token on Ethereum blockchain but don’t know what functions exactly we need to define in those standards. I referred to to understand more about the functions in the ERC-721. So, without any further journey lessons, I will jump into smart contract development. openzeppelin docs To develop our own NFT smart contract, we require Smart contract Ownable It is used to manage the ownership of the contract. By default, the owner of a smart contract is the address from which it is deployed. It has functions that lets transfer ownership of the contract to another address using method. [transferOwnership(newOwner)](https://docs.openzeppelin.com/contracts/2.x/api/ownership#Ownable-transferOwnership-address-) It lets you renounce your ownership of the contract with [renounceOwnership()](https://docs.openzeppelin.com/contracts/2.x/api/ownership#Ownable-renounceOwnership--) It provides modifier to let some functions get executed by the only owner like starting the sale, pausing the contract, Give away NFTs from the contract. [onlyOwner()](https://docs.openzeppelin.com/contracts/2.x/api/ownership#Ownable-onlyOwner--) Smart contract Enumerable721 It extends , so we don’t need our contract to extend ERC721 contract explicitly. ERC721 standards This provides enumerability of all the token ids in the contract as well as all token ids owned by each account. See the functions provided by the . documentation Smart Contract ReentrancyGuard This module helps prevent reentrant calls to a function meaning it makes modifier available, which can be applied to functions to make sure there are no nested (reentrant) calls to them. [nonReentrant](https://docs.openzeppelin.com/contracts/4.x/api/security#ReentrancyGuard-nonReentrant--) Functions marked as may not call one another. nonReentrant Smart Contract Pausable It is also advisable to extend this one which allows child contracts to implement an emergency stop mechanism that can be triggered by an authorized account. This used through inheritance and makes modifiers and available which can be applied to the functions of your contract. whenNotPaused whenPaused We can make our main smart contract extend these smart contracts directly by importing these in our code. The code is found here for Loot Royale Onchain NFT Smart Contract - https://gist.github.com/pranaybathini/52f4ff2da4c3518855264febe7d95739 Let us discuss the functions inside the main smart contract - BattleRoyale.sol Three functions are important. Function to let the users mint NFT Tokens by paying the required amount of price for the NFTs they are minting Function to get the token URI of the NFT. This takes in token Id and gives a JSON with the NFT. Here in our case, it is an SVG image generated from the code - On Chain. No external calls are required. Function to get the amount from the contract address to your own address or any address you want to withdraw. I wrote the function to withdraw to owner's address of the smart contract. NFT Design for on-chain smart contract Here is what one of my NFTs looks like. A simple HTML CSS Design inside svg tag with curved border and it also displays the token ID at the top. It took some time for me to realize that we can include html CSS inside svg tag.  Initially, I took the HTML CSS code and used to convert to SVG but the output svg size is very heavy. this site Another problem I faced while storing this data for design was that the max size of a smart contract cannot be more than bytes. So, I moved the code to another smart contract then to library, just so to reuse it in another contract. This is just one line but took some time since I tried optimizing it first before realizing I can do move this to another contract. Learning++. 24576 Here is the link to SVG Code for the above NFT. Also, you can see my data in the code which is different from loot project. You should have guessed by now where I gotmy data from. Now let’s see what are on-chain vs off-chain NFTs. On-chain vs Off-chain NFTs The difference between on-chain and off-chain NFTs as the name suggests we will be storing all the data related to NFTs on the blockchain itself for on-chain NFTs. In the case of off-chain, I need to provide some external URLs like , ipfs://sha256hash/1.png. https:// somedomain.com In both cases, I need  to return the JSON output file following the NFT metadata standard. A sample IPFS image URL looks like this - ipfs://QmV3yGkzx2Uw3NHPZV9SAMLA58j7LvCFLFYtyfCMBAvstF/2.jpg You can open this in brave browser directly - a pin I have drawn on the art flow mobile app a long time back. If we were to create off-chain NFTs, what would the code look like? Refer to this github gist link for offchain smart contract. I will set the IPFS or HTTPS BASE URI  in the contract when the sale starts or nowadays, the developers are revealing the NFTs after all NFTs are minted. It is simple to write a function to set URI variable and call it once all NFTs are minted. There are two variables Base URI - actual URI for NFTs Blind URI - Till we reveal the NFTs, this image or video will be the same for all the minted NFTs. The URI we should set will be like ipfs://QmV3yGkzx2Uw3NHPZV9SAMLA58j7LvCFLFYtyfCMBAvstF/ When we query, our token Id gets appended to it and Open Sea or any other marketplace can find and display it. Starting steps are to set the contract active, then set the blind URI. Once all NFTs are minted, you can reveal the NFTs minted. The tokenURI method output will look like {
    "image": "ipfs://QmV3yGkzx2Uw3NHPZV9SAMLA58j7LvCFLFYtyfCMBAvstF/1.png",
    "name": "Loot Royale 1",
    "description" : "Some description"
} Compiling and Deploying to blockchain Now we have our contracts, how do we deploy them to the blockchain network. Many blockchains forked Ethereum with added changes to bring DApp development features. You can deploy to any network that supports solidity. Let us deploy this on-chain NFT smart contract to Ethereum’s Ropsten test network. But before that, we need Remix IDE - You can use it online. Simply click . In case you want to run it offline, you can refer to https://remix.ethereum.org/ this blog on how to download it on docker and run it. Metamask wallet  - If you don’t have a metamask wallet, follow If you are using brave, it is inbuilt within the browser. You can access it from your settings. this blog to install metamask wallet in the browser of your choice. Get some Ropsten testnet ether/ Rinkeby testnet ether/ Polygon testnet Matic to deploy the contract on the ropsten network. Change the network to ropsten on metamask. - Ropsten Testnet Faucet https://faucet.ropsten.be/ - Polygon testnet faucet https://faucet.polygon.technology/ If you deploy on Rinkeby testnet or polygon testnet you will be able to see your NFTs on opensea testnetwork. Next steps are same for all the networks. Next steps Copy the contract to your remix IDE. It should look like below. You can select the compiler version to any version above 8.0 But remember this version which you used to compile. This is needed while verifying the contract on the block explorer. In case you don’t know what is a block explorer, refer to this blog to understand in detail. Go to the compiler tab and click on compile. You should see a green tick mark like below. Go to the deploy tab. You should select the contract as BattleRoyale.sol By default, the environment will be Javascript VM. All the transactions will be executed in a sandbox blockchain in the browser. This means nothing will be persisted when you reload the page. The Javascript VM is its own blockchain and on each reload it will start a new blockchain, the old one will not be saved. You need to select Injected Web3 as an environment, which will allow us to inject metamask and deploy to the network selected on metamask. You should be able to see your metamask account and balance in the accounts section. When you click on deploy, you will be prompted twice. First, the CardDesign Library is deployed and then our smart contract. You will receive two metamask notifications once the contracts are deployed. Click on them, you will be redirected to Ropsten block explorer. You can also view the transactions from the activity tab in metamask. Congrats, now the On-chain NFT smart contract - loot royale has been deployed. But how do we interact with it? I will explain in detail how to interact with it from our custom react frontend later. Let’s see how to interact with the contract from the block explorer. FYI, block explorer is also a DApp. Verifying the contract on blockchain Explorer Now, let us verify the contract on the blockchain explorer and interact with it from the explorer itself. Open contract addresses of Card Design Library in one tab (We require this address), Open the contract address of the Loot Royale contract in another tab like below. Click on verify and Publish and fill in the details below. I used 8.7 as a compiler version while deploying from remix, so I am using the same here. Click on continue. Copy the code from remix IDE and paste in the code part. Remove the string from constructor part like below. Enter the library address as below and verify you are not a robot and click on Verify and publish. Now, our contract is verified. It looks like the below image. You should see the functions to read and write to the blockchain. Navigate to the write contract section and click on connect to web3, you will be prompted to connect to a provider like below. Click on Metamask, it will prompt you to connect. Click on connect to web3 again and you should be able to connect explorer with Metamask like below. Now click on mintSingle function, it will an NFT. Enter 0.01 as NFT Price like below. Congratulations. You have successfully minted an NFT. Now, let’s view the token URI. You can go to , connect your wallet and you should be able to see your Loot Royale NFTs. testnets.opensea.io Loot Royale NFTs on Open sea Testnet In the next blog, I will show how to design the frontend for to mint the loot royale NFTs since this blog has become lengthy already. lootroyale.xyz Any feedback is appreciated. In case of any doubts or issues or any new ideas, DM me on Twitter - . Let us learn together. @pranay_bathini Thanks for reading!! This article was also published here

How to Create On-Chain and Off-Chain NFT Collection Smart Contracts

Dear reader, Welcome to the latest edition of the “One More Thing in AI newsletter." For Startup founders and Business Leaders like you who want to get smarter on AI in less than 5 minutes. In this focused edition, we are going to present a few AI startups that caught my eye. Why? It will give you an idea of the art of the possible in the field of AI, especially in your organizations. It might also inspire you to start something on your own! I hope you enjoy this edition. I'd love to hear your feedback (positive or negative). Best regards, Renjit Philip Notable AI Startups Changing the World AI technology is getting super advanced, and startups are using it to shake up different industries in cool ways. Let's check out some of these brilliant companies: Pay Automatically With JustPaid Businesses can find dealing with invoices and payments a hassle. But JustPaid has created an awesome AI system that does it all automatically. Their AI tracks usage makes invoices, sets up customer accounts, and handles payments—all within a company's normal systems. JustPaid started in the US but plans to offer its payment AI everywhere. Robot Farmers Detecting Crop Diseases In places like the UAE, where growing food is tough, Egrobots uses robots and AI to spot crop diseases before they spread. Their robot scouts roam farms collecting data that their AI analyzes. They also have an app that can instantly identify diseases on plants and give farmers advice. This tech could boost food supplies. AI Making Amazing Videos ZhipuAI is working on incredible AI that turns words into videos! This Chinese startup got investments from Alibaba and the government to take on OpenAI's similar Sora tech. While it is excellent for movies and shows, there are worries about using it for fake videos, too. AI Coding Buddies Coding is hard, but Replit made an AI assistant called Teams that helps while you program! It suggests fixes and better ways to write code in real-time on their browser IDE. It's like having an intelligent coding partner, making you a better, faster coder. AI Salesperson's Assistant For salespeople, the SiftHub AI acts like a virtual briefcase loaded with all the latest info on products and companies. With $5.5 million in funding, the company's AI preps sales teams so they can focus on building relationships during client meetings. Better Business Planning with AI Pigment scored a massive $145 million investment in its AI business planning software. The tool combines a company's data to precisely forecast finances and collaborate across departments on strategy. Fun AI Videos for Social Media Higgsfield created an app called Diffuse that uses AI to make animated videos on your phone. This app is perfect for posting engaging videos on TikTok, YouTube Shorts, and more. With $8 million invested, this startup is unleashing AI's video creation magic. These AI startups are completely changing how we work, farm, make videos, and more. The AI revolution has barely started! That is it for this edition of the newsletter. If you subscribe to our email edition, you get our newsletter first, and it stays in your mailbox as a future reference. Until next time, keep learning, applying, and experimenting with AI! Also published here. Dear reader, Dear reader, Welcome to the latest edition of the “ One More Thing in AI newsletter." For Startup founders and Business Leaders like you who want to get smarter on AI in less than 5 minutes . One More Thing in AI newsletter." For Startup founders and Business Leaders like you who want to get smarter on AI in less than 5 minutes In this focused edition, we are going to present a few AI startups that caught my eye. Why? It will give you an idea of the art of the possible in the field of AI, especially in your organizations. It might also inspire you to start something on your own! I hope you enjoy this edition. I'd love to hear your feedback (positive or negative). Best regards, Renjit Philip Renjit Philip Notable AI Startups Changing the World AI technology is getting super advanced, and startups are using it to shake up different industries in cool ways. Let's check out some of these brilliant companies: Pay Automatically With JustPaid Businesses can find dealing with invoices and payments a hassle. But JustPaid has created an awesome AI system that does it all automatically. Their AI tracks usage makes invoices, sets up customer accounts, and handles payments—all within a company's normal systems. JustPaid started in the US but plans to offer its payment AI everywhere. Robot Farmers Detecting Crop Diseases In places like the UAE, where growing food is tough, Egrobots uses robots and AI to spot crop diseases before they spread. Their robot scouts roam farms collecting data that their AI analyzes. They also have an app that can instantly identify diseases on plants and give farmers advice. This tech could boost food supplies. AI Making Amazing Videos ZhipuAI is working on incredible AI that turns words into videos! This Chinese startup got investments from Alibaba and the government to take on OpenAI's similar Sora tech. While it is excellent for movies and shows, there are worries about using it for fake videos, too. AI Coding Buddies Coding is hard, but Replit made an AI assistant called Teams that helps while you program! It suggests fixes and better ways to write code in real-time on their browser IDE. It's like having an intelligent coding partner, making you a better, faster coder. AI Salesperson's Assistant For salespeople, the SiftHub AI acts like a virtual briefcase loaded with all the latest info on products and companies. With $5.5 million in funding, the company's AI preps sales teams so they can focus on building relationships during client meetings. Better Business Planning with AI Pigment scored a massive $145 million investment in its AI business planning software. The tool combines a company's data to precisely forecast finances and collaborate across departments on strategy. Fun AI Videos for Social Media Higgsfield created an app called Diffuse that uses AI to make animated videos on your phone. This app is perfect for posting engaging videos on TikTok, YouTube Shorts, and more. With $8 million invested, this startup is unleashing AI's video creation magic. These AI startups are completely changing how we work, farm, make videos, and more. The AI revolution has barely started! That is it for this edition of the newsletter. If you subscribe to our email edition, you get our newsletter first, and it stays in your mailbox as a future reference. Until next time, keep learning, applying, and experimenting with AI! That is it for this edition of the newsletter. If you subscribe to our email edition , you get our newsletter first, and it stays in your mailbox as a future reference. Until next time, keep learning, applying, and experimenting with AI! subscribe to our email edition Also published here. Also published here . here

Revolutionizing Tech: Notable AI Startups Changing the World

188 Stories To Learn About Analytics

Scientific American, Vol. XXXIX. No. 6. [New Series.], August 10, 1878, by Various, is part of the HackerNoon Books Series. You can jump to any chapter in this book . A VELOCIPEDE FEAT EXTRAORDINARY. here A VELOCIPEDE FEAT EXTRAORDINARY. Two intrepid velocipedists, M. le Baron Emanuel de Graffenried de Burgenstein, aged twenty years and six months, and a member of the Society of Velocipede Sport, of Paris, has accomplished, with M. A. Laumaillé d'Angers, the greatest distance that has been made with a velocipede in France. Leaving Paris on March 16, they returned on the 24th of April, after having traveled a distance of more than three thousand miles. Their route extended through a part of the west, the middle, and the south of France, Italy, and southern Switzerland. They traveled through Orléans, Tours, Poitiers, Angoulême, Bordeaux, Montauban, Toulouse, Montpellier, Marseilles, Toulon, Nice, Menton, San-Remo, Genoa, Turin, Milan, the Simplon—where they barely escaped destruction by an avalanche—Vevay, Berne, Lausanne, Geneva, Dijon, Troy, and Provins. The longest distance that they accomplished in a single day, was between Turin and Milan, a distance of 90 miles, which they made in 9-1/2 hours. Superior Excellence of American Goods. The , of Birmingham, England, remarks with regard to American competition, that "perhaps the most humiliating feature of the business for British manufacturers is the fact that their competitors are prevailing, not through the cheapness, but through the excellence of their goods. Time was when English workmanship ranked second to none, and the names of our great manufacturing firms were a guarantee for the sterling quality of the goods they turned out; but competitions, trades unions, piece work, short hours, and other incidents of the 'march of progress' have altered all that. Complaints, received by hardware merchants from their customers abroad, are not confined to the goods of second class firms. Manufacturers who have obtained a world-wide reputation for their products are frequently convicted of sending out scamped and unfinished work, and they do not venture to deny the impeachment, pleading only that the most vigilant must be sometimes at fault, and that their men, unfortunately, are not to be depended upon. In other cases it is the merchants or their customers who are to blame for the inferior quality of the articles by cutting prices so low as to preclude the possibility of honest work, thinking, probably, that anything is good enough for a foreign or colonial market. But whatever the cause, the fact is now undeniable, that a great deal of the manufactured produce shipped from this country of late years has been of a very low standard, and that the American manufacturers have consequently had an easy task in beating it." Post Petroleum Oils as Lubricators. Oils from petroleum are now produced suitable for nearly every mechanical process for which animal oils have heretofore been used, not excepting those intended for cylinder purposes. A serious objection attaching to the animal oils is present in petroleum. If, through the exhaust steam, some of the oil be carried into the boiler, foaming or priming is the consequence, but the same thing happening in the case of petroleum is rather a benefit than otherwise, for it not only does not cause foaming, but it prevents incrustation or adhesion of the scale or deposit, and this aids in the preservation of the boiler, and is perhaps the best preventive of the many everywhere suggested. Often, in removing the cylinder head and the plate covering the valves of an engine, we see evidences of corrosion or action on the surfaces, differing entirely from ordinary wear, and the engineer is generally at a loss how to account for it. According to the general impression grease or animal oil is the preservative of the metal, and is the last thing suspected of being the cause of its general disintegration. The reason of this is that vegetable and animal oils consist of fatty acids, such as stearic, magaric, oleic, etc. They are combined with glycerin as a base, and, under ordinary conditions, are neutrals to metals generally, and on being applied they keep them from rusting by shielding them from the action of air and moisture. But in the course of time the influence of the air causes decomposition and oxidation, the oils become rancid, as it is called, which is acid, and they act on the metals. What happens at the ordinary temperature slowly goes on rapidly in the steam cylinder, where a new condition is reached. The oils are subjected to the heat of high pressure steam, which dissociates or frees these acids from their base, and in this condition they attack the metal and hence destroy it. This applies as well to vegetable as to oils of animal origin, fish or sperm oil included. Petroleum and oils derived therefrom (generally called mineral oils) are entirely free from this objection. Petroleum contains no oxygen, and hence it cannot form an acid, and therefore cannot attack metal. It is entirely neutral, and so bland that it may be and is used medicinally as a dressing to wounds and badly abraded surfaces where cerates of ordinary dressing would give pain.— Coal Trade Journal. Influence of Light on Plants and Animals. Professor Paul Bert, who has recently devoted a great deal of attention to the study of the influence of light on animals and plants, denies that the leaves of the sensitive plant close on the approach of evening, the same as if they had been touched by the hand. On the contrary, he finds that from 9 in the evening, after drooping, they expand again and attain the maximum of rigidity at 2 in the morning. What is commonly called the "sensitiveness" of plants is but the external manifestations of the influences of light. Professor Bert placed plants in lanterns of different colored glass; those under the influence of green glass drooped in the course of a few days as completely as if placed in utter darkness, proving that green rays are useless, and equal to none at all. In a few weeks all plants without exception thus treated died. It has been proved by the experiments of Zimiriareff that the reducing power of the green matter of plants is proportionate to the quantity of red rays absorbed, and Bert shows that green glass precisely intercepts these colored rays, and that plants exist more or less healthily in blue and violet rays. In the animal world phenomena of a directly opposite nature are found, and of a more complex character. Here the light acts on the skin and the movements of the body, either directly or through the visual organs. M. Pouchet has shown the changes in color that certain animals undergo, according to the medium in which they live. For instance, young turbots resting on white sand assume an ashy tint, but when resting on a black bottom become brown; when deprived of its eyes the fish exhibits no change of color in its skin; the phenomenon, therefore, seems to be nervous or optical. Professor Bert placed a piece of paper with a cut design on the back of a sleeping chameleon; on bringing a lamp near the animal the skin gradually became brown, and on removing the paper a well defined image of the pattern appeared. In this case the light acted directly, and without nervous intervention. If, however, the eye of the chameleon be extracted, the corresponding side of the animal becomes insensible to the influence of the light. Professor Bert's conclusion, therefore, is that the circulation in the transparent layers of the skin must be affected by light. According to Dr. Bouchard a sunstroke is the effect of the direct action of light upon the skin, produced by the blue and violet rays. The heat producing rays have no part in such accidents, as proved by the fact that workmen exposed to intense heats do not feel their fatal effect. Professor Bert, in a series of experiments on a variety of animals, found that none avoided light, but all rather sought it; and the lowest forms, like the highest, absorbed the same rays. As regards intensity of color, however, there was a difference, some being more partial to one ray than another. Thus the microscopic daphne of the pond preferred yellow; violet was less in request; spiders seemed to enjoy blue rather than red rays—so resembling people suffering from color blindness. No two persons are sensible to the same shades or tones, while absorbing the same light; and this would seem to indicate that the retina possesses a selective power. New Mechanical Inventions. An improved Weighing Scale has been patented by Hosea Willard, of Vergennes, Vt. The object of this invention is to economize time in ascertaining the weight of an article by avoiding the necessity for shifting the poise on the scale beam. It consists in providing a scale beam with a number of dishes suspended from different points on said beam, and representing or corresponding with different weights, so that the weight of an article may be ascertained by placing it in one or more of said dishes and observing which dish is depressed. William John, of Rigdon, Ind., has patented an improved Tire Setting and Cooling Apparatus, by which the tire may be set by one person, easily and quickly, without burning the fellies, and without straining the wheel by the unequal cooling of the tire. Joseph A. Mumford, of Avondale, Nova Scotia, Canada, has patented an improved machine for Sawing and Jointing Shingles. This machine cannot be properly described without engravings. It has an ingenious feeding device, and its flywheel carries the jointing knives. Ill-balanced Production. The Philadelphia sensibly remarks that the popular complaint of over-production is a mistake. Though of a few things we make or mine too much, our main trouble arises from not producing enough, in variety if not in quantity. Record "The wants of mankind never can be satisfied. Every new means of supplying a want creates new wants. They grow by what they feed on. As long as humanity is so constituted, over-production, in a general and enlarged sense, is impossible. It is this impossible thing with which the reformers would deal who propose to work fewer hours each day, or fewer hours in the week. The trouble they deplore does not exist; the remedy they propose defeats itself. A man cannot get rid of his load by shifting it from his right hand to his left hand. Production will not be stopped by making men their own employers certain hours in the day or certain days in the week, instead of allowing them to pursue their usual avocations. "The real trouble, which the labor reformers seem incompetent to fathom, is that there is not enough diversity in employments. What is desired is more work in productive enterprises, a more diffused industry, and a closer commercial connection with those countries wherein we can make desirable exchanges both of our raw material and our manufactured products. Every miner that drops his pick and takes up a hoe, every idle man that turns himself into an earner of wages, every person that picks up some loose thread of employment, every capitalist that takes advantage of stagnating industry and cheap material to build a house or beautify or improve a country seat, or set on foot some new process of manufacture, does something toward working out the problem which is puzzling the economists. In good time the surplus iron and coal will be sold; new populations will want new railroads; recuperated capital will gather confidence and take hold of new enterprises, and the whole nation will move forward again to more assured prosperity and to vaster undertakings." Labor in Germany. The consul at Barmen reports that for agricultural labor the pay varies greatly, according to the proximity to or remoteness from manufacturing centers; and ranges from fifty-six cents a day in the neighborhood of Barmen to thirty-one cents a day in the lower Rhine valley, and as low as eighteen cents in parts of Silesia. At Barmen, Crefeld and Düsseldorf, carpenters, coppersmiths, plumbers, machinists and wagonsmiths earn fifty-one to seventy-five cents daily; saddlers and shoemakers forty-seven to fifty-two cents daily; bakers and brewers, with board and lodging, from $1.42 to $2.14 weekly, and without board from sixty cents a day to $4.28 a week; farm hands are paid from $107 to $215 yearly, with maintenance; railroad laborers from fifty-six to eighty-[Pg 90]three cents per day, and as high as ninety-five cents daily for piece work on tunnels; silk weavers can earn $2.15 to $2.85 a week per loom; factory women $2.15, and children $1 a week. Business and wages are very low. In good times wages are eighty per cent higher. The cost of the necessaries of life has increased some fifty per cent in thirteen years, although it is now but little higher than five years ago. A man and wife with two or three children can live in two or three rooms in a poor and comfortless manner for $275 a year, and to support such an establishment all the members have to work ten or twelve hours daily. For a family of six persons the cost is about $7 per week—an amount but few families can earn, as the depression of trade and the reduction of time allow few to do a full week's work, although wages are nominally a trifle higher than five years ago. Petroleum June Review. DRILLING WELL ACCOUNT. The low price of oil and large accumulation of stock in the producing regions have had the effect to lessen operations in this department during the month of June. The total number of drilling wells in all the districts, at the close of the month, was 266, which was 110 less than in the preceding month. Rigs erected and being erected 243, against 309 last month. The number of drilling wells completed during the month was 269, being 151 less than in May. Aggregate production of the new wells was 3,788 barrels, against 6,851 barrels in May. The total number of dry holes developed in the month was 22, against 42 in May. The operators in the great northern field (Bradford district) have curtailed operations to an extent which will compare favorably with the operators in the other portions of the producing regions, as will be seen by the following statement, namely: Number of wells drilling at the close of the month, 187, against 284 at the close of the previous month. Number of drilling wells completed in June, 193, against 346 in May. Number of rigs erected and being erected, 196, against 234 in May. PRODUCTION. The daily average production for the month was 40,575 barrels, being a decrease of 227 barrels. The new wells completed in June failed to make good the falling off of the old ones, by decreasing the daily average 227 barrels. Bradford district shows a daily average production of 16,000 barrels, being an increase of 1,280 barrels over last month. The aggregate production in June of all the other districts combined, with the aid of 76 new wells, decreased the daily average 1,507 barrels. SHIPMENTS. The shipments in June, out of the producing regions, were 174,225 barrels larger than in the preceding month. The total shipments of crude, and refined reduced to crude equivalent, by railroad, river and pipes to the following points, were 1,135,119 barrels: New York took 555,794 bbls. Pittsburg " 153,182 " Cleveland " 239,389 " Philadelphia " 73,426 " Boston " 29,266 " Baltimore " 26,623 " Richmond " 7,000 " Ohio River refiners took 5,200 " Other local points took 45,239 " Total shipments 1,135,119 " Included in the above shipments there were 140,299 barrels of refined from Titusville and Oil City, which is equal to 187,065 barrels of crude.— Stowell's Petroleum Reporter. Remarkable Poisoning of a Lake. A contributor to describes the remarkable poisoning of Lake Alexandrina—one of the bodies of water which form the estuary of the Murray river, Australia. This year the water of the river has been unusually warm and low, and the inflow to the lakes very slight. The consequence has been an excessive growth of a conferva which is indigenous to these lakes and confined to them. This alga, , is very light and floats on the water, except during breezes, when it becomes diffused, and being driven to the lee shores, forms a thick scum like green oil paint. Nature Nodularia spumigera This scum, which is from two to six inches thick, and of a pasty consistency, being swallowed by cattle when drinking, acts poisonously and rapidly causes death. The symptoms of the poisoning are stupor and unconsciousness, falling and remaining quiet (as if asleep), unless touched, when convulsions are induced, the head and neck being drawn back by a rigid spasm, subsiding before death. The poison causes the death of sheep in from one to six or eight hours; of horses, in from eight to twenty-four hours; of dogs, in from four to five hours; and of pigs in three or four hours. A shows the plant is rapidly absorbed into the circulation, where it must act as a ferment, and causes disorganization. As the cattle will not touch the puddle where the plant scum has collected and become putrid, all they take is quite fresh, and the poisoning is therefore not due to drinking a putrescent fluid full of bacteria, as was suggested. post mortem When the scum collects and dries on the banks it forms a green crust. When, however, it is left in wet pools it rapidly decomposes, emitting a most horrible stench, like putrid urine; but previous to reaching this stage it gives out a smell like that of very rancid butter. A blue pigment exudes from this decomposing matter, having some remarkable properties. It is remarkably fluorescent, being red by reflected and blue by transmitted light; it appears to be a product of the decomposition, and allied to the coloring matter found in some lichens. About HackerNoon Book Series: We bring you the most important technical, scientific, and insightful public domain books. This book is part of the public domain. Various (2013). Scientific American, Vol. XXXIX. No. 6. [New Series.], August 10, 1878. Urbana, Illinois: Project Gutenberg. Retrieved https://www.gutenberg.org/cache/epub/19406/pg19406-images.html This eBook is for the use of anyone anywhere at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this eBook or online at , located at www.gutenberg.org https://www.gutenberg.org/policy/license.html

A VELOCIPEDE FEAT EXTRAORDINARY

Scientific American, Volume XXIV., No. 12, March 18, 1871 by Various, is part of the HackerNoon Books Series. You can jump to any chapter in this book . Cosmetics. here Cosmetics. The extensive use of preparations for hiding nature's bloom on the human countenance, and presenting to our view a sort of metallic plaster, suggests the inquiry, "how are these pigments made?" Without going into an unnecessary analysis of the "Bloom of Youth," the "Rejuvenator," the "Corpse Decorator," or the other inventions for destroying the skin, with which the druggists' stores abound, we may state again the fact, always unheeded, that all the detestable compounds are injurious. They are nearly all metallic poisons, and, if there be any that are innocent of this charge, they are in every instance harmful to the health. The color and surface of the skin cannot be changed by any application which does not close the pores; the pores, which are so exquisitely fine that there are millions of them to the square inch, and which must be kept open if a healthy and cleanly body is to be preserved. There is more breathing done through the pores of a healthy person than through the lungs; and we need not remind our readers of a ghastly piece of cruelty once enacted in Paris (that of gilding the body of a child, for a triumphal procession, which killed the subject in two hours), to show that the stoppage, in any degree, of the natural functions of so important an organ as the skin, is injurious. The immediate effect of the use of such compounds is to destroy the vitality of the skin, and to render it, in appearance, a piece of shriveled parchment. We must warn our readers that a temporary and meretricious "bloom" can only be attained at the cost of future freshness and lively appearance, so that a year or two of "looking like paint" is followed by a long period of "looking like dilapidation." About HackerNoon Book Series: We bring you the most important technical, scientific, and insightful public domain books. This book is part of the public domain. Various (2006). Scientific American, Volume XXIV., No. 12, March 18, 1871. Urbana, Illinois: Project Gutenberg. Retrieved https://www.gutenberg.org/cache/epub/19180/pg19180-images.html This eBook is for the use of anyone anywhere at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this eBook or online at , located at . www.gutenberg.org https://www.gutenberg.org/policy/license.html

The extensive use of preparations for hiding nature's bloom on the human countenance

Scientific American Supplement, No. 717, September 28, 1889, by Various, is part of the HackerNoon Books Series. You can jump to any chapter in this book . WALNUT OIL. here WALNUT OIL. By Thomas T. P. Bruce Warren. This oil, which I obtained from the fully ripened nut of the , has so many excellent properties, especially for mixing with artists' colors for fine art work, that I am surprised at the small amount of information available on this interesting oil. Jugluns regia Walnut oil is largely used for adulterating olive oil, and to compensate for its high iodine absorption it is mixed with pure lard oil olein, which also retards the thickening effect due to oxidation. The marc left on expression of the oil is said to be largely used in the manufacture of chocolate. Many people, I am told, prefer walnut oil to olive oil for cooking purposes. The value of this oil for out-door work has been given me by a friend who used it for painting the verandas and jalousies of his house (near Como, Italy) some twenty years ago, and which have not required painting since. In this country, at least, walnut oil is beyond the reach of the general painter, and I do not know that the pure oil is to be obtained as a commercial article, even on a small scale. It was in examining the properties of this and other oils, used as adulterants of olive oil, that I was obliged to prepare them so as to be sure of getting them in a reliable condition as regards purity. The walnuts were harvested in the autumn of 1887, and kept in a dry airy room until the following March. The kernels had shrunk up and contracted a disagreeable acrid taste, so familiar with old olive oil in which this has been used as an adulterant. Most oxidized oils, especially cotton seed oil, reveal a similar acrid taste, but walnut oil has, in addition, an unmistakable increase in viscosity. The nuts were opened and the kernels thrown into warm water, so as to loosen the epidermis; they were then rubbed in a coarse towel, so as to blanch them. The decorticated nuts were wiped dry and rubbed to a smooth paste in a marble mortar. The paste was first digested in CS2, then placed in a percolator and exhausted with the same solvent, which was evaporated off. The yield of oil was small, but probably, if the nuts had been left to fully ripen on the trees without knocking them off, the yield might have been greater. It is by no means improbable that oxidation may have rendered a portion of the oil insoluble. The decorticated kernels gave a perfectly sweet, inodorous, and almost colorless oil, which rapidly thickens to an almost colorless, transparent, and perfectly elastic skin or film, which does not darken or crack easily by age. These are properties which, for fine art painting, might be of great value in preserving the tinctorial purity and freshness of pigments. Sulphur chloride gives a perfectly white product with the fresh oil, but, when oxidized, the product is very dark, almost black. The iodine absorption of the fresh oil thus obtained is very high, but falls rapidly by oxidation or blowing. A curious fact has been disclosed with reference to the oxidation of this and similar oils. If such an oil be mixed with lard oil, olive oil, or sperm oil, it thickens by oxidation, but is perfectly soluble. Such a mixture is largely used in weaving or spinning. Commercial samples of linseed oil, when cold-drawn, have a much higher iodine absorption, probably due to the same cause. Oils extracted by CS2 are very much higher than the same oils, especially if hot-pressed.— Chem. News. About HackerNoon Book Series: We bring you the most important technical, scientific, and insightful public domain books. This book is part of the public domain. Various (2006). Scientific American Supplement, No. 717, September 28, 1889. Urbana, Illinois: Project Gutenberg. Retrieved https://www.gutenberg.org/cache/epub/17755/pg17755-images.html This eBook is for the use of anyone anywhere at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this eBook or online at , located at . www.gutenberg.org https://www.gutenberg.org/policy/license.html

WALNUT OIL

Scientific American Supplement, No. 392, July 7, 1883 by Various, is part of the HackerNoon Books Series. You can jump to any chapter in this book . CEREAL FOODS IN THEIR RELATION TO HEALTH AND DISEASE. here CEREAL FOODS IN THEIR RELATION TO HEALTH AND DISEASE. By F.R. CAMPBELL, A.B., M.D. The cereals are subject to many diseases which retard their development, rendering them unfit for food, and even poisonous. The relation of unwholesome foods to the diseases of the animal body are now being thoroughly studied, recent advances in chemistry and microscopy contributing valuable aid to the prosecution of such investigations. Some enthusiastic advocates of the germ theory of disease believe that many, if not all, the so-called disease germs may be transplanted into the human system with the food ingested. But whatever may be the real truth in regard to this subject, it has been positively demonstrated that many diseases of the human body may be produced by unwholesome food. The specific symptoms produced in man by the various grain diseases are not accurately known, consequently our remarks upon this subject must be of a very general character. Pappenheim divides the diseases of the cereals into two classes, internal and external. The internal diseases are those depending upon conditions of soil, climate, cultivation, etc., and may be neglected in our discussion, as they produce no special disease of the body, only impairing the nutritive value of the grain. The external diseases are of much greater importance, as they probably produce some of the most fatal maladies to which the human race is subject. These external diseases of the cereals are due to parasites, which may be either of an animal or vegetable nature. Among the animal parasites may be mentioned the , which feeds upon the starch cells of the grain. Grain attacked by this parasite was at one time supposed to be injurious to health. weevil, vibrio tritici In 1844 the French Commission appointed to examine grain condemned a large quantity imported with this parasite, but afterward reconsidered their decision and permitted its sale, concluding that it was deficient in nutritive properties, but not otherwise unwholesome. Rust is the most common disease of the cereals, produced by vegetable parasites. Like the other diseases of this class, it is most prevalent in warm, damp seasons. Prof. Hensboro is of the opinion that rust is but an earlier stage of mildew or blight, the one form of parasite being capable of development into the other, and the fructification characteristic of the two supposed genera having been evolved on one and the same individual. Blight is a term loosely applied to a number of parasitic diseases. In it are included mildew, cories, and even rust and smut. The fungi producing these diseases attack the plant and seed at various stages of its growth. The whole kernel is affected, and not merely the external coat, as is sometimes maintained. When blighted grain is sown, the disease recurs the following year, often making it necessary to import new seed before the disease can be eradicated. Various remedies have been used to destroy the spores of these fungi, but all are uncertain and some are dangerous to health. Special machinery and methods have been employed in the mills to separate the mildew from the grain. Some of these succeed in removing the fungi and discoloration from the surface of the grain, but have no effects upon the parts within. Blighted grain is soft, and has an unpleasant taste and smell, and bread made of it is liable to be heavy and sodden. It is undeniable that the use of blighted grain as food is exceeding dangerous to health. It is a well known fact that vegetable parasites may attack animals; the silk worm disease produced by the , being an example. It is stated that the same vegetable parasites which produce plant diseases, when transmitted to the animal body produce special affections, the form and appearance of the germs being altered by their environments. The same germs developed under different conditions of temperature and surrounding medium, assume forms so various that they have been supposed to belong to different species and even different genera. If there is any truth, then, in the germ theory of disease, it is not so very improbable that a fungus which will produce blight in grain may cause cholera or tetanoid fever in an animal. Botrytis baniana Hallier, the famous physiological botanist, observed in 1867 that there was a peculiar disease of the rice plant associated with an epidemic of cholera. Rice plants fertilized with the discharges of cholera patients were affected with blight. A concentrated infusion of the blighted grain would produce changes in all animal substances, blood and albumen being converted into thin odorless products resembling in every respect the material found in the kidneys of cholera patients. The most formidable of the diseases attributed to the use of diseased grain is cerebro-spinal meningitis, commonly known as spotted or blanoid fever. The disease is rare in England, but is frequently epidemic in the United States, in Ireland, and on the Continent. In 1873, in the State of Massachusetts alone, 747 persons died of it, and other epidemics even more fatal have lately occurred in New York and Michigan. The disease is a nervous fever attended with convulsions, the pathological lesion being congestion and inflammation of the membrane of the spinal cord and brain. Dr. Richardson in writing on the nature and causes of spotted fever concludes that it is due to the use of diseased vegetable substances, especially grain, and from a careful analysis of the statistics of this disease reported by the Michigan State Board of Health considers it demonstrated that "under favoring condition for its action diseased grain received as a food is the primary cause of the phenomena which characterize the disease." These views are substantiated by the experiments of Dr. H. Day, who found that by feeding rabbits on unsound grain, spasmodic affections were produced, due to inflammation of the membranes of the spinal cord and brain. In warm climates, pellagra or Italian leprosy is said to be produced by eating diseased maize, which forms the principal article of food among the poorer classes of the rural districts. Pellagra is epidemic in northern Italy and the south of France. The disease is manifested by a redness and discoloration of the exposed parts of the body. It is most active during the hot weather, the inflammation subsiding in the winter, leaving a pigmentation of the skin. Each year the symptoms become more alarming, nervous disorders finally setting in, and a large number die insane. The disease is most prevalent in the country. In the towns, where maize is supplemented by other articles of food, it does not exist. Ergot is a very common disease of the cereals. The fungus producing it was discovered in 1853, but for centuries previous its injurious effects upon the human body were recognized, and it was observed that ergot of rye was the most poisonous. Taken in large doses, ergot will produce nausea, vomiting, diarrhoea, headache, and weakness of the heart. In small repeated doses it will produce contraction of all the unstriped muscles, as those of the blood vessels, the womb, and intestines. Ergotium is the name given to the disease produced by the continued use of grain affected by this fungus. Aitken describes it as "a train of morbid symptoms produced by the slow and cumulative action of a specific poison peculiar to wheat and rye, which produces convulsions, gangrene of the extremities, and death. In countries where rye bread is much used ergotium is sometimes epidemic. This was a frequent calamity before the introduction of suitable purifiers into the mills. There are two varieties of the disease, the convulsive and the gangrenous. The convulsive form begins with tingling of the extremities, drowsiness, and headache, followed by pain in the joints, violent muscular contractions, and death. The gangrenous variety begins with coldness and weakness of the extremities followed by gangrene and sloughing. This form is somewhat more fatal than the convulsive, the mortality of those affected being about 90 per cent. Mouldy grain and bread have also caused poisoning. Prof. Varnell states that "six horses died in three days from eating mouldy oats. There was a large amount of matted mycelium, and this when given to other horses for experiment, killed them within thirty-six hours." The writer has himself seen seven hogs die within a few days while being fed on mouldy corn. Flour which has become stale may produce similar injurious effects, although most of the germs are destroyed in the process of baking. It is quite probable, however, that a poisonous substance is generated by the mould fungus, which cannot be destroyed in this way.-- . Milling World About HackerNoon Book Series: We bring you the most important technical, scientific, and insightful public domain books. This book is part of the public domain. Various (2005). Scientific American Supplement, No. 392, July 7, 1883. Urbana, Illinois: Project Gutenberg. Retrieved https://www.gutenberg.org/cache/epub/8742/pg8742-images.html This eBook is for the use of anyone anywhere at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this eBook or online at , located at . www.gutenberg.org https://www.gutenberg.org/policy/license.html

CEREAL FOODS IN THEIR RELATION TO HEALTH AND DISEASE

Scientific American, Volume XXXVI., No. 8, February 24, 1877 by Various, is part of the HackerNoon Books Series. You can jump to any chapter in this book . Absence of White Color in Animals. here Absence of White Color in Animals. Some very curious physiological facts bearing upon the presence or absence of white colors in the higher animals have lately been adduced by Dr. Ogle. It has been found that a colored or dark pigment in the olfactory region of the nostrils is essential to perfect smell, and this pigment is rarely deficient except when the whole animal is pure white. In these cases the creature is almost without smell or taste. This, Dr. Ogle believes, explains the curious case of the pigs in Virginia adduced by Mr. Darwin, white pigs being poisoned by a poisonous root which does not affect black pigs. Mr. Darwin imputed this to a constitutional difference accompanying the dark color, which rendered what was poisonous to the white colored animals quite innocuous to the black. Dr. Ogle, however, observes that there is no proof that the black pigs eat the root, and he believes the more probable explanation to be that it is distasteful to them, while the white pigs, being deficient in smell and taste, eat it, and are killed. Analogous facts occur in several distinct families. White sheep are killed in the Tarentino by eating , while black sheep escape; white rhinoceros are said to perish from eating ; and white horses are said to suffer from poisonous food where colored ones escape. Now it is very improbable that a constitutional immunity from poisoning by so many distinct plants should, in the case of such widely different animals, be always correlated with the same difference of color; but the facts are readily understood if the senses of smell and taste are dependent on the presence of a pigment which is deficient in wholly white animals. The explanation has, however, been carried a step further by experiments showing that the absorption of odors by dead matter, such as clothing, is greatly affected by color, black being the most powerful absorbent, then blue, red, yellow, and lastly white. We have here a physical cause for the sense-inferiority of totally white animals which may account for their rarity in nature. For few, if any, wild animals are wholly white. The head, the face, or at least the muzzle or the nose, are generally black. The ears and eyes are also often black; and there is reason to believe that dark pigment is essential to good hearing, as it certainly is to perfect vision. We can therefore understand why white cats with blue eyes are so often deaf—a peculiarity we notice more readily than their deficiency of smell or taste.— , 1876. hypericum criscum euphorbia candelabrum Dr. Wallace, British Association About HackerNoon Book Series: We bring you the most important technical, scientific, and insightful public domain books. This book is part of the public domain. Various (2006). Scientific American, Volume XXXVI., No. 8, February 24, 1877. Urbana, Illinois: Project Gutenberg. Retrieved https://www.gutenberg.org/cache/epub/19406/pg19406-images.html This eBook is for the use of anyone anywhere at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this eBook or online at , located at www.gutenberg.org https://www.gutenberg.org/policy/license.html

Absence of White Color in Animals

Of Copying

Scientific American Supplement, No. 799, April 25, 1891 by Various, is part of the HackerNoon Books Series. You can jump to any chapter in this book . MARBLE AND MOSAIC. here MARBLE AND MOSAIC. By T.R. SPENCE. I do not propose to enter into any historical details as to the first and subsequent application of mosaics. In a general sense we understand mosaic as a combination of various more or less imperishable materials—fixed together by cement or other adhesive substances—and laid over walls, floors, etc., with a view to permanent decorative effect. The substance of the tesseræ is of many kinds, namely, glass, cheap and precious marbles, hard stone, and burnt clay, these mentioned being mainly in use for architectural purposes. For decorative schemes we collect as many gradations of color as are obtainable in such durable materials in their natural or manufactured state, and thus form a color palette which we regard in the same sense as a painter would his pigments. Of course, the first proceeding is to prepare a design on a small scale, which shall embrace your notions of color only. Then follows a full-sized cartoon, which I need hardly add shall embrace your best efforts in drawing. A tracing is made of the latter and transferred to sheets of cardboard. This cardboard is cut to the size of certain sections of your design, and, for convenience, should not be more than, say, 20 in. square. Of course, it will not always be square, but will bear the same relation to your complete cartoon as a map of the counties would to that of all England. Now, working from the small design (of color), the tesseræ are cut to the forms required, laid face downward, and glued on to the cardboard sections containing your enlarged cartoon. When the design is all worked out on these sections they are ready for fixing on walls or floor by laying them home on a float of cement. When the cement sets, the cardboard sticking to the face is washed off, and the joints of tesseræ flushed over with cement and cleaned off, leaving all joints filled up level. There are other processes used for the same end. The technical processes need not occupy our attention at present. There is one process that may appeal to you, and that is executing the work by floating on a limited expanse of cement, and sticking on the tesseræ at once. It has the advantage of enabling the artist or architect to see the effect of his efforts under the fixed conditions of light and height. in situ I shall confine myself to vitreous or glass mosaic, which for durability, extended scales of primary colors and their numerous semi-transparent gradations is unequaled by any substance yet used for wall or floor decoration. I am surprised, having all these fine qualities, it is not more used by architects. If you require proofs of its triumphs, go to St. Mark's, of Venice, and stand under its mellow golden roof. There you will find its domes and vaulted aisles, nave and transepts entirely overlaid with gold mosaic, into which ground is worked—in the deepest and richest colors and their gradations that contemporary manufacturers could produce—subjects selected from the creation down to the life of Christ, in addition containing a complete alphabet of early Christian symbolism. The roof surfaces being one succession of over-arching curves become receptive of innumerable waves of light and broad unities of soft shadows, giving the whole an incomparable quality of tone and low juicy color. Never use your gold but on curved or undulating surfaces. Flat planes of gold only give the effect of a monotonous metallic yellow, and can never be beautiful, owing to the absence of the variations that come with waves of shadow. By letting out the reins of imagination we might feel that in this a tenth century Giorgione has given off the mental impressions of all the golden autumn of his life. His material gave him an advantage over his great followers of the fifteenth and sixteenth centuries, insomuch that glass has a living and glowing quality of light not existing in the somewhat clouded purity of oil or fresco. In St. Mark's we have an example of the superb treatment in deepest and most Titianesque scales applied to curved forms, but to find a similarly complete example of the use of lighter tones and on flat surfaces, we must turn to Ravenna. I can give you no adequate description of the wall mosaics of Ravenna. In the sense of delicate color they remind me of some of the subtile harmonies of many of the finest works of the modern French school—of the Impressionists and others who combine that quality with a true instinct for design. In standing before them you feel that the Dagnan Bouverets, the Mersons, the Cazins, the Puvis de Chavannes, etc., of the fifth century have had a hand in the conception and realization of the beautiful compositions to be found on the nave walls of the two churches of St. Appollinare Nuovo and St. Appollinare in Classe. Here all the scales are of delicate degrees of light tones, supreme in their beauty, completeness, and, most important to us, their true decorative instinct. In the Baptistery we find what I may term a third essay in color, by weaving in rich, dark, and glowing colors on figures and bold sinuous forms of ornament in such a skillful and judicious manner that the whole dome seems to be alive with harmonies, although they are mostly primaries. As you know, rules for the disposition of color are futile, yet some details that struck me as eminently satisfactory may interest you. In all cases the tesseræ are of small dimensions, about a quarter of an inch square. The stucco joints are large and open, surfaces far from level, but undulating considerably. The tesseræ stick up in parts, brilliant edges showing. Absence of flatness gives play to the light. The gray of the stucco joints brings the whole composition together, serving as cool grays in a picture to give tender unity. Gold, apart from backgrounds and large surfaces, is used very cleverly in small pieces in borders of garments, and more especially in thin outlines to make out the drawing and certain flowing forms of ornament. Brilliant pieces of glass actually moulded at the kiln into forms of jewels add brilliancy to crowns, borders, etc. These stick boldly out from the surface. I noticed in the Baptistery below the springing of the dome a frieze about 2 ft. 6 in. deep, having the ground entirely in black, through which was woven in thin gold lines a delicate foliated design. This, in conjunction with the upper surfaces in dark, rich color, had a most delightful effect. We, as students, can learn most from the Ravenna examples, for great are the needs of light and silvery color in this country, where gray and gloomy days far outnumber those in which the sun gives liberally of his light. I may say, in passing, as our subject is really a matter of decoration, that our nineteenth century efforts in this direction are all of a somewhat gloomy tendency. We fill our rooms with imitations of somber Spanish leather, stain and paint our woodwork in leathery and muddy tones, to arrive at what is now a sort of decorator's god. Quaintness is the name of that god. Many are the sins for which he has to answer. Had we not better worship a deity called beauty, whose place is a little higher up Parnassus? Why should we not in our endeavors attempt in some measure to transfix the brilliant harmonies that follow the sun in his liberal and gracious course? This muddy quaintness is certainly pleasant for brief periods, when lamps are low and fire light gilds and deepens its parts. Turn the sunlight on these so-called triumphs of the modern decorator's art, and then you feel the lack of many a phase of color that might have been borrowed from the thousand and one examples that in nature he vivifies and makes brilliant. Referring again to the Ravenna mosaics, I can only add that at the present day an extended palette of colored glass is available. The technical difficulties are not great, and there is no question as to the fine qualities of design and color that are to be obtained in this material. The great point in this, as in all other schemes of decoration, is the art, the mental quality of conception, and the sense of color and fitness. If we hold the precious heritage of an artist's mind—that divine and rare something which gives form, color, and completeness to a story, a dream or a vision—then very little difficulty follows in making vitreous mosaic a valued servant in the realization of a fine creation. It is the function of architects to design suitable spaces for color decoration, so bound in by dignified mouldings and other details of his constructive art, in such a manner that the addition of decorative color shall in no way mar the scheme of his complete work, but shall (under these well ordered distributions) have set on them the seal and crown of color which is inseparable from a perfect piece of architecture. In such spaces he may dream his dreams, tell his stories, and stamp on them for centuries his subtilest and divinest thoughts. May I not urge that to such spaces must be given the best that is in you? for once placed so shall they remain unchanged through generations, time being powerless to add any mellow garment of tone or softening quality whatever. I mistook the title of the subject in thinking that it was mosaic only, and at the last moment found it was marble and mosaic. However, the same dominant principles shall underlie the treatment of marble. It is a question of the finer instincts for form and color. In recent years the demand for choice decorative materials has been the means of opening out many marble quarries all over the world. Transit being easy, a large scale of varieties is available. One fine addition is the Mexican onyx. My feeling is that the most beautiful marbles are those where the soft and sinuous veins melt and die into the general body, comparatively sharp markings dying right away at the edges into innumerable gradations. Marbles having strong and hardly marked veins present great difficulties in distribution. If they are near, they offend you with their coarseness; and, placed at a distance, the hard vein lines have very little decorative value. I should say use these in narrow slips, with very little moulded profile or as parts of intazzio. Mouldings should be specially designed for different marbles. I should say mainly on the principle of sudden contrasts; that is, large members with very little curve bound with members very small in detail, thus obtaining sharp lines, having little surface to be influenced or distorted by the veined markings, and serving to sharpen up and give form to the broader members (which show the color qualities of the marble), much as you sharpen up an ink drawing by underlining. These small members serve the architect's purpose for the expression of vertical and horizontal lines, and where decisive and cutting shadows are required in the composition of his work. If delicate carving forms part of your design, I should say statuary is the best, as you have no veins to distort your detail. I need hardly add that economy should be studied in using precious marbles, without injuring the durability of the work. Contours may be built up in thin sections. Intazzio is a beautiful form of treating marble on an inexpensive ground. Gem-like effects may be obtained by inlaying with smaller pieces, following such ornamental forms as your inventive brains shall dictate. Perhaps the pockets of your clients will be the chief dictator. Heraldic emblazonings, inlaid in marble, are highly effective. The conditions of the heraldry necessitate the use of many varieties, but in such small quantities that on a large simple field they are rarely out of harmony. In addition they map out a large and interesting variety that will save the worry of creation of designs coming entirely from your own brain, and you know the worry of an architect's life makes him hail with pleasure at times a rest from the strain of creation. This heraldic work may be seen to perfection in the chapel of the tombs of the Medici at Florence. At the Pitti Palace are some tables which you may know where marble intazzio can no further go. Alabaster does not appeal to me, it is somewhat sugary in results. If you are fortunate enough to have a sculptor who is a sort of nineteenth century Donatello, let him work his will on statuary or such restful marble. The celebrated monument in the church of S. Giovanni Paulo, at Venice, which Ruskin says is the finest monument in the world, if my recollection serves me correctly, is in white marble, and its beauty comes entirely from the sculptor's art. Such monuments give you much better than any words of mine ample suggestions for marble treatment. I may quote such names as Nicolo Pisano and Verocchio. Photos of some of their work I have brought. Note Pisano's beautiful white altar at Bologna, and Mina de Fiesole's work in Florence. They all show the sculptor as supreme. Why should not we encourage individual young sculptors more? Give them portions of your work in which they can put all the fervor and enthusiasm of young manhood. Their powers may not be ripe, but they possess a verve and intensity that may have forever fled when in later years the imagination is less enthusiastic and the pulses slower. I am sure there are many young sculptors now wanting commissions who have been trained at the academy, and better still, in the best French schools. I maintain that the contemporary French school of sculpture is in its line equal to any school of sculpture that has ever existed, not excepting that of Phidias or that of the Italian Renaissance of the fifteenth and sixteenth centuries. I believe history will confirm this. Why not give these men an opportunity, and help on the movement to found a truly English school of sculpture, rather than give all such work to trading firms of carvers, who will do you any number of superficial feet, properly priced and scheduled, and in the bills of quantities, of any style you please, from prehistoric to Victorian Gothic? Of course, this is our British way of founding a great school. There is one method of treatment that appeals to me very strongly, and that is the application of colored metals to marble, more especially bronze and copper. I may quote as a successful example near the Wellington Memorial at St. Paul's. Another suggestion—although it is not used in combination with marble, but it nevertheless suggests what might be done in the way of bronze panels—that is, the Fawcett Memorial, by Gilbert, in the west chapel at Westminster Abbey. A paper recently read before the Architectural Association, London.— . From the Architect About HackerNoon Book Series: We bring you the most important technical, scientific, and insightful public domain books. This book is part of the public domain. Various (2004). Scientific American Supplement, No. 799, April 25, 1891. Urbana, Illinois: Project Gutenberg. Retrieved https://www.gutenberg.org/cache/epub/11649/pg11649-images.html This eBook is for the use of anyone anywhere at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this eBook or online at , located at . www.gutenberg.org https://www.gutenberg.org/policy/license.html

MARBLE AND MOSAIC

WATER SUPPLY OF SMALL TOWNS

Scientific American, Volume XXXVI., No. 8, February 24, 1877 by Various, is part of the HackerNoon Books Series. You can jump to any chapter in this book . The Lost Arts in New York here THE LOST ARTS IN NEW YORK. While the objects of ancient art contained in the Castellani collection, recently placed on exhibition in the Metropolitan Museum of Art in this city, are individually of great rarity and archæological value, they derive additional importance from the fact that, viewed conjunctively as a collection, they represent connected histories of two great industrial arts extending over many centuries. Both in the work of the goldsmith and of the potter, we are enabled to trace progress from the earliest stages up to a period when the greatest skill was attained, and even subsequently into the era of decadence. In both industries, we find that ancient and mediæval workmen possessed knowledge which we do not possess; and among Signor Castellani's treasures may be seen handiwork which is the embodiment of two lost arts, the secrets of which the modern world, with all its infinitely superior wisdom, has not yet rediscovered. The productions, in the Castellani collection, of precious metal workers dating from prehistoric epochs, the exact dates of which are wholly unknown, and covering the long period ending in the thirteenth century, are represented by the contents of some twenty cases. The first three of these receptacles bear no dates. The ornaments which they contain are of bronze, amber, silver, and glass (the latter having become converted into opalescent silicic acid), and were found in Præneste (modern Palestrina, Italy), and in the territory which was ancient Etruria. Case No. 4 bears date 700 B.C., and here is a rich treasure of primitive Etruscan and Phœnician ornaments of gold, adorned with granulated work. Signor Castellani considers that the workmanship of these objects is so perfect that it is impossible at the present time to explain the process of execution, and very difficult to imitate it. The ornaments are of two kinds—those for ordinary use and those for funereal purposes. The first are massive, and might be worn for years without injury; the others are extremely delicate. All are made of the purest gold, and their decoration evinces the most consummate skill and taste on the part of the artist. There is, for example, a small flask, shaped something like an antique wine jar, and about five inches in height. It is of beaten gold, and is covered with a pattern intended to imitate the similarly shaped designs of variegated glass of the Græco-Phœnician period. This pattern is entirely produced by minute globules of metal soldered to the surface in tiers of zigzag or Vandyke patterns. Another specimen is a strip of gold covered with granulated lines and bearing a row of birds in relief. On other ornaments are exquisitely carved heads and flowers, produced apparently by hammering on the reverse of the object, but with a delicacy and precision of touch which is simply marvelous. The closest students of this ancient handiwork are entirely at a loss to understand how the processes of melting, soldering, and wire drawing, which were employed in the art, were performed. Modern workmen have failed in their attempts exactly to imitate the old ornaments; and it is certain that the secret of the mechanical agents, whereby it was possible to separate and join pieces of gold hardly perceptible to the naked eye, is lost. Signor Castellani has taken great pains to solve the problem, reading all the treatises of mediæval goldsmiths, inquiring of all classes of Italian jewelers, and experimenting with all kinds of chemicals, in the hope of finding the solder wherewith the minute grains were attached to the surface of the metal. At last he found some of the old processes still employed in a remote district, hidden in the recesses of the Apennines, far from the great towns. Bringing away a few workmen, he gave them much more instruction, and at last succeeded, not perhaps in equalling, but certainly in rivalling the ancient productions. We question whether the Etruscans used fire at all in their soldering, as it would be almost an impossibility to keep the excessively fine tools necessary for the work at a proper heat. Mr. Joshua Rose offers the plausible suggestion that a cold flux was employed, with which the workman followed the lines or dots of his pattern. Then the gold granules were possibly sprinkled over the surface, and adhered only to the solder, the superfluous grains being brushed off after the solder had set. There is also a fragment of a finely woven fabric, made of threads of pure gold, found on the body of a woman in a tomb at Metapontum. This is without doubt the material to which the Psalmist refers in speaking of "the King's daughter" having "clothing of wrought gold;" and in the Pentateuch there is reference to gold threads being used upon looms. As we follow the various objects in the twenty cases above mentioned, the decline of the goldworker's art when the use of enamels came into vogue is evidenced. Continuing on to later periods, the decadence is more marked under the successors of Alexander. In Rome, under the emperors, we find gold used as a mere setting for precious stones, and finally the collection terminates with examples of workmanship of the time of Charlemagne, when the workmen had lost their cunning, and the noble metal had been altogether debased to secondary uses. The second instance where a lost art is exemplified in Signor Castellani's collection is in the glazing of the Gubbio majolica. We have not space here to review the magnificent series of ancient specimens of pottery in detail; and thus it will suffice to say that, beginning with some of the earliest pieces made by the Arabs when they occupied Sicily, from the twelfth to the sixteenth century, the collection presents examples of all the finest types of later mediæval art. Gubbio, where the peculiar kind of majolica above noted was made, is a small town once in the territory of the dukes of Urbino; and in the sixteenth century it became famous for its pottery. This was attributable to the talent of one man, Giorgio Andreoli, who is reputed to have invented the wonderful luster characteristic of the Gubbio ware. The body of majolica is mere common clay; and after the piece is finished on the wheel, it is dried and burnt in a furnace. After the biscuit thus prepared has been dipped in the glaze, the colors are applied on the soft surface of the latter, and the vitrifying process fuses all into a glossy enamel of the color of the pigment. This is still the common practice; and we mention it merely to show that to his pigment and glaze Andreoli must have added some third substance, which rendered the enamel capable of reflecting white light as blue, red, green, or yellow light—in other words, of giving the object a luster of a color wholly different from the tints of the pigment. He evidently could produce any desired color at will, and the effects gained are indescribably beautiful. The Castellani collection contains 130 superb specimens, which glow like jewels. In one, the scene of the nativity of Christ is provided with the figures in low relief, and the exquisite cerulean lustre is imparted to give the effect of moonlight. The rarest pieces are those of which the luster is a delicate green. Some blaze with yellow, as if of gold; others exhibit the brilliancy of the ruby; while others resemble the interior of the pearl oyster shell. Whether this sheen is produced by polarization of the light in some manner, or whether it is at all analogous to fluorescence, is yet to be decided. The impression of the surface with fine microscopic lines might produce an iridescence, but not separate and clearly defined hues. The ware was intended for ornamental purposes, not for household use; and it was suspended against the rich, dark tapestries of the period with which walls were covered, thus aiding, as it were, in illuminating the apartment with its exquisite radiance. About HackerNoon Book Series: We bring you the most important technical, scientific, and insightful public domain books. This book is part of the public domain. Various (2006). Scientific American, Volume XXXVI., No. 8, February 24, 1877. Urbana, Illinois: Project Gutenberg. Retrieved https://www.gutenberg.org/cache/epub/19406/pg19406-images.html This eBook is for the use of anyone anywhere at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this eBook or online at , located at www.gutenberg.org https://www.gutenberg.org/policy/license.html

THE LOST ARTS IN NEW YORK

Debian GNU/Linux: Guide to Installation and Usage by John Goerzen and Ossama Othman is part of the HackerNoon Books Series. You can jump to any chapter in this book . Advanced Topics here 13. Advanced Topics By now, you should have a strong base for which to build your GNU/Linux skills on. In this chapter we cover some very useful information regarding some advanced GNU/Linux features. 13.1 Regular Expressions A regular expression is a description of a set of characters. This description can be used to search through a file by looking for text that matches the regular expression. Regular expressions are analogous to shell wildcards (see section 6.6 on page [*]), but they are both more complicated and more powerful. A regular expression is made up of text and metacharacters. A metacharacter is just a character with a special meaning. Metacharacters include the following: . * [] - ^ $. If a regular expression contains only text (no metacharacters), it matches that text. For example, the regular expression “my regular expression” matches the text “my regular expression,” and nothing else. Regular expressions are usually case sensitive. You can use the egrep command to display all lines in a file that contain a regular expression. Its syntax is as follows: egrep ’regexp’ filename1 ... The single quotation marks are not always needed, but they never hurt. For example, to find all lines in the GPL that contain the word GNU, you type egrep ’GNU’ /usr/doc/copyright/GPL egrep will print the lines to standard output. If you want all lines that contain freedom followed by some indeterminate text, followed by GNU, you can do this: egrep ’freedom.*GNU’ /usr/doc/copyright/GPL The . means “any character,” and the * means “zero or more of the preceding thing,” in this case “zero or more of any character.” So .* matches pretty much any text at all. egrep only matches on a line-by-line basis, so freedom and GNU have to be on the same line. Here’s a summary of regular expression metacharacters: . Matches any single character except newline. * Matches zero or more occurrences of the preceding thing. So the expression a* matches zero or more lowercase a, and .* matches zero or more characters. [characters] The brackets must contain one or more characters; the whole bracketed expression matches exactly one character out of the set. So [abc]matches one a, one b, or one c; it does not match zero characters, and it does not match a character other than these three. ^ Anchors your search at the beginning of the line. The expression ^The matches The when it appears at the beginning of a line; there can’t be spaces or other text before The. If you want to allow spaces, you can permit 0 or more space characters like this: ^ *The. $ Anchors at the end of the line. end$ requires the text end to be at the end of the line, with no intervening spaces or text. [^characters] This reverses the sense of a bracketed character list. So [^abc] matches any single character, except a, b, or c. [character-character] You can include ranges in a bracketed character list. To match any lowercase letter, use [a-z]. You can have more than one range; so to match the first three or last three letters of the alphabet, try [a-cx-z]. To get any letter, any case, try [a-zA-Z]. You can mix ranges with single characters and with the ^metacharacter; for example, [^a-zBZ]means “anything except a lowercase letter, capital B, or capital Z.” () You can use parentheses to group parts of the regular expression, just as you do in a mathematical expression. || means “or.” You can use it to provide a series of alternative expressions. Usually you want to put the alternatives in parentheses, like this: c(ad|ab|at)matches cad or cab or cat. Without the parentheses, it would match cad or ab or at instead \ Escapes any special characters; if you want to find a literal *, you type *. The slash means to ignore *’s usual special meaning. Here are some more examples to help you get a feel for things: matches cope, cape, caper. c.pe c\ .pe matches , c.per. c.pe sto*p matches stp, stop, stoop. car.*n matches carton, cartoon, carmen. xyz.* matches xyz and anything after it; some tools, like egrep, only match until the end of the line. ^The matches The at the beginning of a line. atime$ matches atime at the end of a line. ^Only$ matches a line that consists solely of the word Only—no spaces, no other characters, nothing. Only Only is allowed. b[aou]rn matches barn, born, burn. Ver[D-F] matches VerD, VerE, VerF. Ver[^0-9] matches Ver followed by any non-digit. the[ir][re] matches their, therr, there, theie. [A-Za-z][A-Za-z]* matches any word which consists of only letters, and at least one letter. It will not match numbers or spaces. 13.2 Advanced Files Now that you have a basic understanding of files, it is time to learn more advanced things about them. 13.2.1 The Real Nature of Files: Hard Links and Inodes Each file on your system is represented by an inode (for Information Node; pronounced “eye-node”). An inode contains all the information about the file. However, the inode is not directly visible. Instead, each inode is linked into the filesystem by one or more hard links. Hard links contain the name of the file and the inode number. The inode contains the file itself, i.e., the location of the information being stored on disk, its access permissions, the file type, and so on. The system can find any inode if it has the inode number. A single file can have more than one hard link. What this means is that multiple filenames refer to the same file (that is, they are associated with the same inode number). However, you can’t make hard links across filesystems: All hard references to a particular file (inode) must be on the same filesystem. This is because each filesystem has its own set of inodes, and there can be duplicate inode numbers on different filesystems. Because all hard links to a given inode refer to the same file, you can make changes to the file, referring to it by one name, and then see those changes when referring to it by a different name. Try this: cd; echo "hello" > firstlink cd to your home directory and create a file called firstlink containing the word “hello.” What you’ve actually done is redirect the output of echo (echo just echoes back what you give to it), placing the output in firstlink. See the chapter on shells for a full explanation. cat firstlink Confirms the contents of firstlink. ln firstlink secondlink Creates a hard link: secondlink now points to the same inode as firstlink. cat secondlink Confirms that secondlink is the same as firstlink. ls -l Notice that the number of hard links listed for firstlink and secondlinkfiles!inodes is 2. echo "change" >> secondlink This is another shell redirection trick (don’t worry about the details). You’ve appended the word “change” to secondlink. Confirm this with cat secondlink. cat firstlink firstlink also has the word “change” appended! That’s because firstlink and secondlink refer to the same file. It doesn’t matter what you call it when you change it. chmod a+rwx firstlink Changes permissions on firstlink. Enter the command ls -l to confirm that permissions on secondlink were also changed. This means that permissions information is stored in the inode, not in links. rm firstlink Deletes this link. This is a subtlety of rm. It really removes links, not files. Now type ls -l and notice that secondlink is still there. Also notice that the number of hard links for secondlink has been reduced to one. rm secondlink Deletes the other link. When there are no more links to a file, Linux deletes the file itself, that is, its inode. All files work like this—even special types of files such as devices (e.g. /dev/hda). A directory is simply a list of filenames and inode numbers, that is, a list of hard links. When you create a hard link, you’re just adding a name-number pair to a directory. When you delete a file, you’re just removing a hard link from a directory. 13.2.2 Types of Files One detail we’ve been concealing up to now is that the Linux kernel considers nearly everything to be a file. That includes directories and devices: They’re just special kinds of files. As you may remember, the first character of an ls -l display represents the type of the file. For an ordinary file, this will be simply -. Other possibilities include the following: ddirectory
lsymbolic link
bblock device
ccharacter device
pnamed pipe
ssocket Symbolic Links Symbolic links (also called “symlinks” or “soft links”) are the other kind of link besides hard links. A symlink is a special file that “points to” a hard link on any mounted filesystem. When you try to read the contents of a symlink, it gives the contents of the file it’s pointing to rather than the contents of the symlink itself. Because directories, devices, and other symlinks are types of files, you can point a symlink at any of those things. So a hard link is a filename and an inode number. A file is really an inode: a location on disk, file type, permissions mode, etc. A symlink is an inode that contains the name of a hard link. A symlink pairs one filename with a second filename, whereas a hard link pairs a filename with an inode number. All hard links to the same file have equal status. That is, one is as good as another; if you perform any operation on one, it’s just the same as performing that operation on any of the others. This is because the hard links all refer to the same inode. Operations on symlinks, on the other hand, sometimes affect the symlink’s own inode (the one containing the name of a hard link) and sometimes affect the hard link being pointed to. There are a number of important differences between symlinks and hard links. Symlinks can cross filesystems. This is because they contain complete filenames, starting with the root directory, and all complete filenames are unique. Because hard links point to inode numbers, and inode numbers are unique only within a single filesystem, they would be ambiguous if the filesystem wasn’t known. You can make symlinks to directories, but you can’t make hard links to them. Each directory has hard links—its listing in its parent directory, its . entry, and the .. entry in each of its subdirectories—but to impose order on the filesystem, no other hard links to directories are allowed. Consequently, the number of files in a directory is equal to the number of hard links to that directory minus two (you subtract the directory’s name and the . link). comparing!hard links and symlinks You can only make a hard link to a file that exists, because there must be an inode number to refer to. However, you can make a symlink to any filename, whether or not there actually is such a filename. Removing a symlink removes only the link. It has no effect on the linked-to file. Removing the only hard link to a file removes the file. Try this: cd; ln -s /tmp/me MyTmp cd to your home directory. ln with the -s option makes a symbolic link - in this case, one called MyTmp that points to the filename /tmp/me. ls -l MyTmp Output should look like this: lrwxrwxrwx 1 havoc havoc 7 Dec 6 12:50 MyTmp -> /tmp/me The date and user/group names will be different for you, of course. Notice that the file type is l, indicating that this is a symbolic link. Also notice the permissions: Symbolic links always have these permissions. If you attempt to chmod a symlink, you’ll actually change the permissions on the file being pointed to. chmod 700 MyTmp You will get a No such file or directory error, because the file /tmp/me doesn’t exist. Notice that you could create a symlink to it anyway. mkdir /tmp/me Creates the directory /tmp/me. chmod 700 MyTmp Should work now. touch MyTmp/myfile Creates a file in MyTmp. ls /tmp/me The file is actually created in /tmp/me. rm MyTmp Removes the symbolic link. Notice that this removes the link, not what it points to. Thus you use rm not rmdir. rm /tmp/me/myfile; rmdir /tmp/me Lets you clean up after yourself. symlinks!removing Device Files Device files refer to physical or virtual devices on your system, such as your hard disk, video card, screen, and keyboard. An example of a virtual device is the console, represented by /dev/console. There are two kinds of devices:character and block. Character devices can be accessed one character at a time. Remember the smallest unit of data that can be written to or read from the device is a character (byte). Block devices must be accessed in larger units called blocks, which contain a number of characters. Your hard disk is a block device. You can read and write device files just as you can from other kinds of files, though the file may well contain some strange incomprehensible-to-humans gibberish. Writing random data to these files is probably a bad idea. Sometimes it’s useful, though. For example, you can dump a postscript file into the printer device /dev/lp0 or send modem commands to the device file for the appropriate serial port. /dev/null /dev/null is a special device file that discards anything you write to it. If you don’t want something, throw it in /dev/null. It’s essentially a bottomless pit. If you read /dev/null, you’ll get an end-of-file (EOF) character immediately. /dev/zero is similar, except that you read from it you get the \0 character (not the same as the number zero). Named Pipes (FIFOs) A named pipe is a file that acts like a pipe. You put something into the file, and it comes out the other end. Thus it’s called a FIFO, or First-In-First-Out, because the first thing you put in the pipe is the first thing to come out the other end. If you write to a named pipe, the process that is writing to the pipe doesn’t terminate until the information being written is read from the pipe. If you read from a named pipe, the reading process waits until there’s something to read before terminating. The size of the pipe is always zero: It doesn’t store data, it just links two processes like the shell |. However, because this pipe has a name, the two processes don’t have to be on the same command line or even be run by the same user. You can try it by doing the following: cd; mkfifo mypipe Makes the pipe. echo "hello" > mypipe & Puts a process in the background that tries to write “hello” to the pipe. Notice that the process doesn’t return from the background; it is waiting for someone to read from the pipe. cat mypipe At this point, the echo process should return, because cat read from the pipe, and the cat process will print hello. rm mypipe You can delete pipes just like any other file. Sockets Sockets are similar to pipes, only they work over the network. This is how your computer does networking. You may have heard of “WinSock,” which is sockets for Windows. We won’t go into these further because you probably won’t have occasion to use them unless you’re programming. However, if you see a file marked with type son your computer, you know what it is. 13.2.3 The proc Filesystem The Linux kernel makes a special filesystem available, which is mounted under /proc on Debian systems. This is a “pseudo-filesystem” because it doesn’t really exist on any of your physical devices. The proc filesystem contains information about the system and running processes. Some of the “files” in /proc are reasonably understandable to humans (try typing cat /proc/meminfo or cat /proc/cpuinfo); others are arcane collections of numbers. Often, system utilities use these to gather information and present it to you in a more understandable way. People frequently panic when they notice one file in particular— /proc/kcore —which is generally huge. This is (more or less) a copy of the contents of your computer’s memory. It’s used to debug the kernel. It doesn’t actually exist anywhere, so don’t worry about its size. If you want to know about all the things in /proc, type man 5 proc. 13.2.4 Large-Scale Copying Sometimes you may want to copy one directory to another location. Maybe you’re adding a new hard disk and you want to copy /usr/local to it. There are several ways you can do this. The first is to use cp. The command cp -a will tell cp to do a copy preserving all the information it can. So, you might use cp -a /usr/local /destination However, there are some things that cp -a won’t catch[1]. So, the best way to do a large copy job is to chain two tar commands together, like so: [1] Sparse files and hard links are two examples. tar -cSpf - /usr/local | tar -xvSpf -
-C /destination The first tar command will archive the existing directory and pipe it to the second. The second command will unpack the archive into the location you specify with -C. 13.3 Security Back in section 7.1 on page [*], we discussed file permissions in Linux. This is a fundamental way to keep your system secure. If you are running a multi-user system or a server, it is important to make sure that permissions are correct. A good rule of thumb is to set files to have the minimum permissions necessary for use. If you are running a network server, there are some other things to be aware of as well. First, you ought to uninstall or turn off any network services you’re not using. A good place to start is the file /etc/inetd.conf; you can probably disable some of these. For most network services, it’s also possible to control who has access to them; the /etc/hosts.allow and /etc/hosts.deny files (documented in man 5 hosts_access) can control who has access to which services. You also ought to keep up-to-date with patches or updates to Debian; these can be found on your nearest Debian FTP mirror. Some other commonsense rules apply: ◼ Never tell anyone your password. ◼ Never send your password in cleartext across the Internet by using something like telnet or FTP. Instead, use encrypted protocols or avoid logging in remotely. ◼ Avoid using root as much as possible. ◼ Don’t install untrusted software, and don’t install it as root. ◼ Avoid making things world-writable whenever possible. /tmp is one exception to this rule. While this is probably not of as much use to somebody not running a server, it is still pays to know a bit about security. Debian’s security mechanism is what protects your system from many viruses. 13.4 Software Development with Debian Debian makes a great platform for software development and programming. Among the languages and near-languages it supports are: C, C++, Objective-C, Perl, Python, m4, Ada, Pascal, Java, awk, Tcl/Tk, SQL, assembler, Bourne shell, csh, and more. Writing programs is beyond the scope of this book, but here are some of the more popular development programs in Debian: gcc The GNU C Compiler, a modern optimizing C compiler. g++ The C++ compiler from the gcc line. cpp The C preprocessor from gcc. perl The Perl interpreter. Perl is a great “glue” language. gdb GNU Debugger, used to debug programs in many different languages. gprof Used for profiling, this program helps you to find ways to improve the performance of your programs. emacs GNU Emacs is a programmers’ editor and IDE. as The GNU Assembler. About HackerNoon Book Series: We bring you the most important technical, scientific, and insightful public domain books. This book is part of the public domain. John Goerzen and Ossama Othman (2004). Debian GNU/Linux : Guide to Installation and Usage. Urbana, Illinois: Project Gutenberg. Retrieved https://www.gutenberg.org/cache/epub/6527/pg6527-images.html This eBook is for the use of anyone anywhere at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this eBook or online at , located at . www.gutenberg.org https://www.gutenberg.org/policy/license.html

Advanced Topics

Let's learn about via these 52 free stories. They are ordered by most time reading created on HackerNoon. Visit the to find the most read stories about any technology. Image Processing /Learn Repo 1. How to Print images with TSPL and JavaScript How to Print images with TSPL and JavaScript 2. How Computer Vision Turns Images Into Arrays How Images are turned into arrays in Computer Vision 3. How To Convert WebP Images Into Other Image Formats If you are having trouble loading an image on the web, do not worry because you always have the option of converting it into another format that is more widely 4. What Is Digital Image Processing? With digital image processing, users can enhance digital pictures, extract useful information, and save them in different formats. 5. 5 Best Online Tools to Compress and Optimize Your Images Here are the 5 Best Online Tools to Compress and Optimize Your Images. 6. This Is How Easy it Is to Read and Display Images Working with images is more and more popularized; we are going to take dive into this field, first with the basics and starting with an open CV library. 7. JPEG Sucks but Deep Learning Can Help It Improve In this post, I’ll show how you can reduce image sizes by an additional 20–50% with a single line of code. 8. How Image to Text Technology Can Ease Your Writing Process To collect the information from the images, you do not have to write it down manually.  Instead of that, you can use image-to-text technology. 9. How to Create a High-Performing QR Code Scanner in Flutter In this article, I will take you on a journey through the process of creating a scanner that is not only functional but also visually stunning. 10. Implementing Handwritten Text Recognition to Automate Clinical Trials Manual processing of data (overviews, summaries,study reports) is significantly slowed down and inefficient.AI-driven handwritten text recognition is a solution 11. How To Optimize Images in Django Using ImageEngine Learn how to optimize images in Django using an easy-to-use ImageCDN. ImageEngine automatically serves your images in next-gen formats on the global CDN. 12. 3 Simple Ways to Optimize Your Images and Improve Core Web Vitals Image performance plays a huge role in #CoreWebVitals, which in turn play a huge role in SEO. We'll show 3 quick and simple ways to optimize images. #webperf 13. AVIF Is the Next-Gen Image Format You Will Hear a Lot More About The AVIF Format is the next-gen image format based on the AV1 video encoding format, that reduces file size, while improving #CoreWebVitals. Learn how. 14. New Gatsby Plugin Image: One Of The Coolest Innovations At GatsbyConf 2021 March is off to a great start with the coming & going of GatsbyConf 2021 and the big announcement of Gatsby v3.0! Let's talk about the new Gatsby Image Plugin! 15. 5 Ways to Load Less Imagery to Increase Ranking and Client Happiness Improve your ranking by both search engines and humans by not forcing the client to download unnecessary imagery. 16. Building a FastAPI OCR Microservice In this article, I will try to explain basic ideas on how to create your own OCR service for free, using python, fastAPI, tesseract, redis, celery and docker. 17. Speed up AMP pages with an Image CDN It takes a lot of time and effort to build a profitable website that offers great user experience on any given device type. When you start from a clean slate, you have to take care of everything on your own: browser compatibility, performance, responsive design, discoverability and a whole slew of other factors. 18. Will Generative Models Be The Next Machine Learning Boom? Machine Learning is a rapidly growing and very complex field of study. Generative Models might prove to be a new breakthrough that will make a new boom. 19. How to Integrate an Image CDN in Your React Application One of the most crucial maxims that I internalized during my career in web engineering is that every technical decision embodies tradeoffs. No matter the benefits, you’ll always face certain costs and restrictions: be it creating an abstraction in your code, scaling a distributed data store or choosing between web and mobile app format for the initial product launch. 20. Introducing CropScore: An Image Cropper for Content Creators ✂✨ If you are a content creator, the chances are you have come across stretched, shrank, non-centered or pixelated images after the posting of your material. 21. Improve Core Web Vitals Using Lazy Loading and BlurHash Lazy loading is an important way to improve your PageSpeed Insights. Combined with #Blurhash, you can improve load times. #lazyloading #corewebvitals #SEO 22. Automatic Image Optimization Using the Nuxt Image Component with imgix See how you can use imgix and the Nuxt Image Component to accelerate page speed, simplify image workflow, and transform images at scale. 23. 5 Common Mistakes to Avoid When Adding Images to Your Website We spend a lot of time crafting the perfect pitch in our blog posts and web copies. However, when it comes to visuals, many skimp out and add just about any relevant image available – without getting into the details. 24. How to Implement Gaussian Blurs A Gaussian blur is applied by convolving the image with a Gaussian function. We’ll take the Gaussian function and we’ll generate an n x m matrix. 25. Feature/Permission Policies Overview It's already challenging enough to create a website that is blazing fast, adheres to all the latest best practices and offers optimal experience for various network conditions and device types. As the website and its codebase evolves over time, it can become even harder to maintain the desired user experience over time. To prevent UX deterioration, it’s often a good idea to place guardrails which ensure that crucial website elements, such as images, hold to a certain criteria. In this article, we are going to look at a robust mechanism which helps to steer your website in the right direction - an HTTP header called Feature Policies. 26. Canva Business Model Breakdown: Product, Revenue, Competition, and The Big Question What is Canva? Canva is a software product that helps designers of any skill level to create media 10x faster. 27. Improve the User Experience in Your Mobile App by Using Low-light Enhancement Tech This article introduces how to use AI technology to solve the image quality of Low-Light Images and improve user experience. 28. A Python Library for Face Detection and Extraction with OpenCV Using HOG/Neural Network Many people, including me, use a combination of libraries to work on the images, such as: OpenCV itself, Dlib, Pillow etc. But this is a very confusing and problematic process. Dlib installation, for example, can be extremely complex and frustrating. 29. How Online Classifieds Can Innovate With Immersive Technologies What solutions allow app developers to embed immersive content displaying into a mobile app. 30. Making a Music Visualization with P5JS I had the immense pleasure of attending several creative coding workshops on April 4th. They were streamed live on the SpacyCloud Twitch channel. There were additional sessions involving Hydra, Raspberry Pi, Haskell, and more. However for this post I want to focus on the first session which was a P5JS tutorial. In this post I hope to translate the P5JS tutorial into a written format, for posterity and to share what I learned. I'm going to review what was taught in the live session. Hopefully SpacyCloud will have another live stream in the future so I can catch up on what I missed. Here is the landing page for the event schedule. 31. What it Means to be a Creative Coder Programmers rarely agree on whether or not coding is a creative profession. My interest in coding always stemmed from what I could create with the code. Seeing an interesting visual result from my efforts is usually the most satisfying part. Most programmers are less concerned with how their app looks and more concerned with the functionality. Usually, as long as the app works the way it is supposed to, most programmers are satisfied. 32. PULSE: Photo Upsampling Makes Blurry Faces 60 Times Sharper The new PULSE: Photo Upsampling algorithm transforms a blurry image into a high-resolution image. 33. Dall-E May Be Awesome, but It Still Can't Count. OpenAI's "Dall-E" artificial intelligence can be very frustrating for some professional uses. Here are a few things that Dall-E just can't seem to do. 34. Obtaining Data From Images Using Exif: How To Automate The Process A how-to guide for automating the EXIF data from batch image files. 35. I Found The One Tool To Sort All Your Pictures Like A Boss For years I have been frustrated and I wanted to find a proper way of sorting my pictures. I had photos coming from several devices, and made manual copies on my laptop and on my external hard drive. I ended up with tons of folders and a lot of duplicates. 36. How is Artificial Intelligence Transforming Life Sciences? 4 Main Ways AI has been revolutionizing the life sciences by using its ability to process data quickly to assist with diagnoses and other important medical procedures. 37. Essential Guide to Image Processing with WebAssembly Simple image manipulations with WebAssembly and AssemblyScript in the web browser. 38. Filestack And Other OCR APIs OCR software enables the digitization of essential data in paper documents and photographs. 39. Image Optimization and Transformation with Cloudinary The web is now dominated with more visual content than ever hence the need to consider ways of delivering these images with the smallest possible file size while maintaining optimal visual quality. 40. How to Keep Your e-Store Core Web Vitals Healthy with an Image CDN As we now know, how users interact with your page is just as influential as what is on your pages when it comes to user satisfaction. Search engines, like Google, have wised up to this dynamic by introducing user experience as a significant component in their ranking factors. 41. The Best Ways to Improve Your NFT Marketplace Performance In NFT marketplaces,  page experience, SEO, and credibility can all determine success. Here are 7 ways to improve performance through visual media optimization. 42. Understanding Basic Image Processing Algorithms [A Hands-on JavaScript Tutorial] We've had a lot of digital image processing tools for a long time: Photoshop, Lightroom, GIMP, PhotoScape, and many more. However, in the past few years, one became popular among non-expert users due to its easiness of use and social features: Instagram. Have you ever wondered how Instagram filters work? It is actually pretty simple matrix operations! So simple we can build our own without any external library, just pure and simple HTML + JS. Let's build one now. 43. Use Cases and Roll-Out Tips for Image Recognition in Retail Heavily shattered by the pandemic, the retail sector is on the lookout for innovation. 44. An In-Depth Look at Image Scaling Concepts Considerations upon image sizing for web display 45. Image Processing Algorithms: Adjusting Contrast And Image Brightness Let's take a look at the common approaches for implementing image contrast adjustments. We'll go over histogram stretching and histogram equalization. 46. How to Build an Image Search Engine to Find Similar Images After reading this article, you will be able to create a search engine for similar images for your objective from scratch 47. Intro to Image Processing in Python with Pillow Pillow is Python Imaging Library that is free and open-source an additional library for the Python programming language that adds support for opening, manipulating, and saving in a variety of extension. 48. ColorDetection Module: Python  Color Detection Algorithms Images. That's it. Images. As a point of practicality, take a fashion designer (as a forum member vividly described to me at one point). You are given an image or have an image at your disposal that simply tickles your curiosity and want to incorporate it in one of your new lines. Let's swerve a little into the genetics section. Given a petri dish image for instance, with pigmented bacteria or similar organisms, and you would like to find the abundance of that organism or organisms in this specific image. Get the gist? 49. A Quick Guide to Image Processing in Computer Vision Using OpenCV The image processing library which stands for Open-Source Computer Vision Library was invented by intel in 1999 and written in C/C++ 50. High Quality 8x Upscaling with AI! Have you ever had an image you really liked and could only manage to find a small version of it that looked like this image above on the left? How cool would it be if you could take this image and make it twice look as good? It’s great, but what if you could make it even four or eight times more high definition? Now we’re talking, just look at that. 51. How To Identify Trees with Deep Learning Idea / inspiration 52. How To Resize an Image Correctly in JavaScript JavaScript implementation of so-called Seam Carving algorithm for the content-aware image resizing and objects removal. Dynamic programming approach is applied Thank you for checking out the 52 most read stories about Image Processing on HackerNoon. to find the most read stories about any technology. Visit the /Learn Repo

52 Stories To Learn About Image Processing

Please, don’t tell me you’re still using to debug your application. console.log Ok, everyone does that, sometimes I use console logs too… BUT Chrome has a perfectly working debugger and there’s no configuration required, it just… works. Let me show you: https://youtu.be/t1aEXEvYzvM?embedable=true Or if you prefer reading, here's a summary of what the video is about (but let me recommend you watch the demo in the video). If you never used a debugger, imagine being able to run the code line by line, where you can see all values of your variables at any given time, you can run some extra code to validate your assumptions, you can pause the code only if a condition is met and much more! Ok cool, but how? I’m Leonardo and I talk every week about Web Development and Open Source. Today, let’s see together the Chrome Debugger. Accessing the debugger On Chrome, you can press or right-click on the page and select “Inspect” to open the developer tools. F12 You already know this, but most often you use the Console or the Network tab, but there’s much more than that. To access the debugger, you can click on the “Sources” tab and then on the left, you’ll see all the files that compose your application. From here you can either navigate to the file you want to debug or you can use the search bar to find it. A smart way is with the command palette (Cmd + P on Mac, which should be Ctrl + P on Windows) and then type the name of the file you want to debug. From here you can click on the line number to add a breakpoint and the code will pause when it reaches that line. Using the debugger; statement Alternatively, you can add a statement in your code. When you switch to the browser and you use your app, you will see that nothing happens. debugger; However, if you have the developer tools open, you’ll see that the debugger will pause the execution of the code on that line. This can be useful if you want to debug a specific part of your code and you want a quick shortcut to add a breakpoint from your editor, but please don't forget to remove it before committing and pushing your code. Breakpoints If you're not too familiar with debuggers, I already mentioned breakpoints without explaining what they are... but it's not much more complicated than what I already said. In short, you tell the debugger that you want your code execution to pause when it reaches a specific line... and that's it! On Chrome, the browser will pause and from there you'll be able to manually control the execution of the code... and do some more cool stuff I'll explain in a moment. Last call, you can watch it ! on video Conditional breakpoints The name is self-explanatory, but I'll explain it with an example. for (let i = 0; i < 100; i++) {
  const winner = calculateWinner(players[i]);
  winner.doSomething();
} I want to debug the function but only for the 87th iteration of the loop. With a regular breakpoint I would have to pause and resume the execution of the code 86 times... not ideal. calculateWinner Instead, I can add a conditional breakpoint and tell the debugger to pause only if . i === 87 You can add a condition to a breakpoint by right-clicking on it and selecting "Conditional Breakpoint". As simple as that, but reeeally powerful! Logpoints But console logs? I can't live without them! Ok ok, you can set special breakpoints that are actually logpoints, it's the option right below conditional breakpoints in the menu. This means that instead of pausing the execution of the code, the debugger will just log a message in the console. Advantages? You don't need to spread a ton of console.logs in the code that you would need to remove later, to begin with! Removing a logpoint, as well as other breakpoints, really quick. How? Read the next chapter 👇 Removing breakpoints You can remove a breakpoint by clicking on it. If you want to remove all breakpoints, you can click on the "Deactivate breakpoints" button on the top right. This doesn't actually them, but it deactivates them so you can reactivate everything in a single click. remove In any case, from the Breakpoints tab you can enable/disable and even remove breakpoints in a nice overview. Event listeners If breakpoints, conditional breakpoints, logpoints and the statement are not enough, I don't know what else you might be looking for. debugger Oh wait, it's in the title of this chapter: event listeners. You can add special breakpoints that are triggered only when a specific event is fired. To name one, you can add a breakpoint that is triggered only when you click on an element, as long as there's an event listener attached to it. Building a React app? You press a button and the execution will pause on the first line of the function you attached to the event. onClick Using Chome's debugger Ok, at this point you can't really say you don't know how to launch the debugger or that it's long or complicated. There are so many different ways of pausing the code exactly at the point you need. Now, cool, but what can you do once there? Let's see some cool tricks ;) Values The first thing you'll notice is that if you move your mouse over a variable, you'll see its value. This is already a huge improvement over console logs as you can see all of them without having to dig through a wall of text in the logs. There's also the Scope tab that shows you all the variables in the current scope, grouped in Block, Local, Scope, Module and Global. Watch If you want to keep an eye on a specific variable, you can add it to the Watch tab and it will be there for you to check at any time. But this doesn't work only for variables, you can also add expressions. For example, you can add and it will show you the name of the player at the current iteration of the loop, or if you're manipulating an array you can do and it will show you the names of all the players. players[i].name players.map(p => p.name) Last example, you can write a boolean expression like and it will show you if the condition is true or false while you step through the code. players[i].name === 'Leonardo' Call stack The Call Stack tab shows you the current stack of function calls. This is useful to understand how you got to the current point in the code. For example, you have a function that is called from many different places and you want to know which one is calling it at the moment. On the call stack you can exactly see that, all the previous functions that led the execution to the current one. Moving through time and space Ok maybe the title is a bit too much, but you can do some cool stuff with the debugger to control the execution of the code. Resume The first one is the Resume button. This will resume the execution of the code until the next breakpoint. If there are no more breakpoints, it will just run until the end. You will find yourself using it quite often, for example if you have just one breakpoint to peek at the current state, or if the breakpoint was mostly to validate that the code was executed at all. Step over On the second podium for usage you'll probably find the Step over button. This will execute the current line and then pause again on the next one. If the current line is a function call, it will execute the function and pause on the next line after the function call. Step into The Step into button is similar to the previous one, but instead of executing the current line, it will execute the function call and pause on the first line of the function. Step out The Step out button is the opposite of the previous one. It will execute the current function and pause on the line after the function call. Conclusion And that's it! This was just the tip of the iceberg, there are many more things you can do with the debugger, but I think this is enough to get you started and to make you curious to learn more. After all these cool features, are you gonna continue using console log? Here’s my answer, yes, because I’m lazy. Or at least, if it’s only ONE console log to print a value once, yeah, why not, but as soon as you find yourself writing TWO console logs, or looking at the same log two or three times… think about the debugger. It will save you quite some time. I tried to describe this tool and add some screenshots, but this was kind of a dynamic demo. The video already shows some cool tricks, but now it's your turn to try it out and see what you can do with it. Just use it for some days and you'll find yourself using it more and more. Thanks for reading, and happy debugging! 🎉 Also published . here

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