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Anvil

How to build a web UI with Python Anvil lets you build your app’s front-end entirely in Python - no HTML, CSS or Javascript required. You can build your UI by dragging and dropping components in Anvil’s visual designer or by adding components using Python code: Let’s look at how you can use the to create a user interface by turning this app into a “hello world” app that says hello to your users. Anvil editor In the middle of the Anvil IDE is the which is split into the Design View and the Code View. On the right of the Anvil editor you will find the . Form Editor Toolbox You can drag and drop components, like , from the toolbox to build your user interface. This hello world app will also need a for users to enter their name: Labels TextBox To configure components, you can edit their on the right hand side in the . This includes both the information the component displays and its styling: properties Properties Panel Every component is a Python object, so you can also set the component’s properties in the Code View: Form Editor’s All components have they can raise. For example, when a user of your app clicks a component it raises a click event. We can create a Python method in the Code View to be called when this happens. In your Button’s click method, you can call Anvil’s function to display an alert that says hello to your users: events Button alert Now you can click run to test your app and it’s interface. Your users can now enter their name and clicking the button displays the alert: say hi Using the drag and drop designer isn’t your only option for building user interfaces in Anvil. You can also create and add components to your user interface directly in code: Anvil comes with all the - buttons, text boxes, drop-downs, tables, and so on. And if that’s not enough, you can create your own and share them with other applications. usual UI components custom components To learn more about creating user interfaces with Anvil, why not get started with our 10 minute Feedback Form Tutorial? >>> Get started Build your own app with Anvil If you’re new here, welcome! is a platform for building full-stack web apps with nothing but Python. No need to wrestle with JS, HTML, CSS, Python, SQL and all their frameworks – just . Anvil build it all in Python >>> Try Anvil

How to Make a Web App User Interface with Python

Cómo hacer una interfaz de usuario de una aplicación web con Python

Prague, Czech Republic, Nov 28, 2023, BTCWire Wake is a Python-based Solidity development and testing framework with built-in vulnerability detectors. It was used in audits by Ackee Blockchain and is now being open-sourced and free to use for everyone. Security experts are on high alert, as history shows that hack risks increase as market activity rises. Open-source tooling like Wake empowers application builders to conduct swift and thorough checks for code vulnerabilities. Battlefield-proven audit tool goes open-source , a team of smart contract auditors and creators of community tools, introduces Wake, a Python-based development and testing framework for Solidity and cross-chain fuzzing with a proven track record of stopping bugs. Ackee Blockchain Wake’s features include a development and testing framework, a fuzzer, vulnerability detectors, and printers. Wake was previously used in smart contract audits for , , and and helped the auditors find critical, high, and medium bugs. The firm has announced it will make the tool open-source to contribute to a safer blockchain space. performed by Ackee Blockchain IPOR Axelar Solady Security experts on alert as market activity rises As DeFi activity rises, hackers see more lucrative targets and grow emboldened. In bull markets, projects often rush to ship product updates, creating a high demand for experienced smart contract auditor services. In the peak of the 2021 bull market, projects were typically quoted three month+ audit wait times by reputable firms. They then face a difficult decision to delay launches amid frenzied “land grabs” or launch with hastily conducted audits, increasing security risks. After a week when crypto funds saw their highest inflows since the 2021 bull market and DeFi volumes rose by approximately 50%, security experts are on higher alert. Wake’s release is timely - it allows application developers to expertly test the smart contracts of DEXs or any protocol that plugs into their service or upon which they are reliant. Designed to generate fewer false positives and reduce manual audit time On top of being the testing framework, Wake allows users to run static analysis. It has a set of ready-to-use high-precision vulnerability and code quality detectors and ready-to-use printers for extracting and pretty-printing useful information such as smart contract control flow and inheritance graphs. “A common problem of static analysis tools is a high false-positives ratio requiring extra manual investigation time. Our philosophy is to include only the most precise detectors and reduce all noise that creates extra overhead,” - Josef Gattermayer, CEO and co-founder of Ackee Blockchain. Wake underwent performance , namely Hardhat, Brownie, and Ape, on three different development chains – Anvil, Ganache, and Hardhat. Wake proved to be the fastest Python framework. testing with other frameworks The new release of Wake allows the customization of detectors and printers. It also allows third parties to create and implement their custom printers and detectors. The newest version also introduced Github action for automatically executing detectors in a pipeline. “The low false-positive rate, fastest industry test execution, and ready-made GitHub action make Wake an ideal candidate for CI/CD integration in every project” - Josef Gattermayer, CEO and co-founder of Ackee Blockchain. Wake powers , a popular Visual Studio Code Solidity extension that does syntax highlighting and detections from Wake vulnerability and code quality detectors and provides instant feedback to the developers using the extension access to all references of a symbol across the whole project. Tools for Solidity About Wake Wake is a Python-based development and testing framework for Solidity and cross-chain fuzzing with a proven track record of stopping bugs created by , which became possible thanks to a grant Ackee Blockchain received from Coinbase in 2022. Ackee Blockchain To learn more, please visit . getwake.io | | Website Twitter Telegram About Ackee Blockchain Ackee Blockchain is a team of security researchers auditing top-tier protocols: Safe, 1inch, Axelar, LayerZero, Trader Joe, or CoW Protocol. Ackee Blockchain is backed by the largest VC fund focused on blockchain and DeFi in Europe, RockawayX, and received grants from the Ethereum Foundation, Tezos Foundation, Coinbase, and Solana Foundation. Ackee Blockchain’s mission is to build a stronger blockchain community by sharing knowledge: the team runs a free certification course , and teaches at the Czech Technical University in Prague. This mission is also fulfilled in initiatives such as the ERC-7512 draft, the development of the Wake toolkit, and the development of the open-source fuzzer for Solana. School of Solidity School of Solana | Website Twitter For media inquiries or further information, please contact marketing@ackeeblockchain.com

Wake Testing Tool for Solidity is Now Open Sourced for the Blockchain Dev Community

সলিডিটির জন্য ওয়েক টেস্টিং টুল এখন ব্লকচেইন দেব সম্প্রদায়ের জন্য ওপেন সোর্স

Das Wake Testing Tool für Solidity ist jetzt Open Source für die Blockchain Dev Community

La herramienta de prueba Wake para Solidity ahora es de código abierto para la comunidad de desarrolladores de Blockchain

L'outil de test Wake pour Solidity est désormais open source pour la communauté des développeurs Blockchain

सॉलिडिटी के लिए वेक टेस्टिंग टूल अब ब्लॉकचेन डेव कम्युनिटी के लिए ओपन सोर्स है

Solidity の Wake テスト ツールがブロックチェーン開発コミュニティ向けにオープンソース化されました

Solidity용 Wake 테스트 도구는 이제 블록체인 개발자 커뮤니티를 위해 오픈 소스로 제공됩니다.

A ferramenta Wake Testing for Solidity agora é de código aberto para a comunidade de desenvolvedores Blockchain

Инструмент Wake-тестирования для Solidity теперь открыт для сообщества разработчиков блокчейна

Solidity için Uyanma Testi Aracı Artık Blockchain Geliştirici Topluluğu için Açık Kaynaklı

Công cụ kiểm tra Wake cho Solidity hiện có nguồn mở cho cộng đồng nhà phát triển Blockchain

Solidity 唤醒测试工具现已向区块链开发社区开源

Scientific American, Vol. XXXVII.—No. 2. [New Series.], July 14, 1877 by Various, is part of the HackerNoon Books Series. You can jump to any chapter in this book . BOOT AND SHOE MACHINERY. here BOOT AND SHOE MACHINERY. No manufacturers have taken greater advantage of the ingenuity of the mechanical engineer than the American boot and shoe makers. Nearly every operation in the complex process of evolving finished boots from the plain skins of leather is the object of a special class of machinery; and for several years past, we have weekly chronicled the patenting of several improvements in the devices for effecting some of the numerous operations. We present herewith a series of eight labor-saving machines of the most approved construction, which we select from Knight's "American Mechanical Dictionary."[1] Published in numbers by Messrs. Hurd & Houghton, New York city. Fig. 1 is a shoe-edge trimmer, in which the shoe is mounted on a jack, the carriage of which has a motion of translation and rotation communicated to it: so that, while the side of the sole is being trimmed, the shoe is fed longitudinally against the knife, but at the toe and heel is rotated beneath it. The knife is universally jointed, to permit the hands of the operator to determine the different bevels cut. ![Boot and Shoe Machinery Fig. 2 ](https://cdn.hackernoon.com/images/gQK8BrKBD4ehL3obNS4vfM2m8RB2-i6a3w33.jpeg) Fig. 2 is an ingenious little machine for placing the eyelets of the lace holes in position, and fastening them. The eyelets are fed, one by one, from the reservoir at the top, down the inclined ways, and are seized at the foot between the plunger and anvil, and they are riveted in their proper places in the shoe or strip of leather, which is held and fed by the operator. Fig. 4 is a machine for pressing together the "lifts" which compose a boot or shoe heel, thus dispensing with the handiwork of the hammer and lapstone. The bed is adjusted vertically by a screw to any thickness to which the blank heel may be built; and the plunger is brought down by the depression of the treadle with such force as to compact the lifts together. Fig. 5 shows a heel-pricking machine. When the lifts of the heel are fairly pressed together by the appliance shown in Fig. 4, the pricking machine pierces the necessary holes through all the lifts at once by a gang of awls. The compressed heels are first secured together by tacking, and then placed on the platen; and the plunger, with its gang of awls, descends with great force. Fig. 5 shows a heel-pricking machine. When the lifts of the heel are fairly pressed together by the appliance shown in Fig. 4, the pricking machine pierces the necessary holes through all the lifts at once by a gang of awls. The compressed heels are first secured together by tacking, and then placed on the platen; and the plunger, with its gang of awls, descends with great force. Fig. 6 is a heel trimmer, known in the trade as the Coté trimmer. The shoe is held stationary by the treadle clamp; and the knife stock, which is centrally pivoted to the outer plate or jaw bearing upon the tread lift, is then grasped in the hands of the operator, and moved to give a sweeping cut to trim the heel. Fig. 7 is a machine for pressing boot soles. Beneath the crosshead of the press is a swinging bed, on each end of which is a form, in order that a shoe may remain under pressure upon one while the operator is placing another shoe on the other. The pressure is given by the treadle, which brings down the upper platen on the channeled sole. 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 (2012). Scientific American, Vol. XXXVII. —No. 2. [New Series.], July 14, 1877. Urbana, Illinois: Project Gutenberg. Retrieved https://www.gutenberg.org/cache/epub/38481/pg38481-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

BOOT AND SHOE MACHINERY

On the Economy of Machinery and Manufactures by Charles Babbage is part of the HackerNoon Books Series. You can jump to any chapter in this book . Of Price as Measured by Money here Chapter 17. Of Price as Measured by Money 201. The money price at which an article sells furnishes us with comparatively little information respecting its value, if we compare distant intervals of time and different countries; for gold and silver, in which price is usually measured, are themselves subject, like all other commodities, to changes in value; nor is there any standard to which these variations can be referred. The average price of a certain quality of different manufactured articles, or of raw produce, has been suggested as a standard; but a new difficulty then presents itself; for the improved methods of producing such articles render their money price extremely variable within very limited periods. The annexed table will afford a striking instance of this kind of change within a period of only twelve years. Prices of the following articles at Birmingham, in the undermentioned years Description 1818 1824 1828 1830 s. d. s. d. s. d. s. d. Anvils cwt 25 0 20 0 16 0 13 0 Awls, polished, Liverpool gross 2 6 2 0 1 6 1 2 Bed-screws, 6 inches long gross 18 0 15 0 6 0 5 0 Bits, tinned. for bridles doz. 5 0 5 0 3 3 2 6 Bolts for doors, 6 inches doz. 6 0 5 0 2 3 1 6 Braces for carpenters, with 12 bits set 9 0 4 0 4 2 3 5 Buttons, for coats gross 4 6 6 3 3 0 2 2 Buttons, small, for waistcoats gross 2 6 2 0 1 2 0 8 Candlesticks, 6 in., brass pair 2 1 1 2 0 1 7 1 2 Curry-combs, six barred doz. 2 9 2 6 1 5 0 1 1 Frying-pans cwt 25 0 21 0 18 0 16 0 Gun-locks, single roller each 6 0 5 2 1 10 1 6 Hammers. shoe, No. 0 doz. 6 9 3 9 3 0 2 9 Description 1818 1824 1828 1830 s. d. s. d. s. d. s. d. Hinges, cast-butts, 1 inch doz. 0 10 0 71/2 0 31/4 0 21/4 Knobs, brass, 2 inches for commodes doz. 4 0 3 6 1 6 1 2 Latches for doors, bright thumb doz. 2 3 2 2 1 0 0 9 Locks for doors, iron rim, 6 inches doz. 38 0 32 0 15 0 13 6 Sad-irons and other castings cwt 22 6 20 0 14 0 11 6 Shovel and tongs, fire-irons pair 1 0 1 0 0 9 0 6 Spoons, tinned table gross 17 6 15 0 10 0 7 0 Stirrups, plated pair 4 6 3 9 1 6 1 1 Trace-chains cwt 28 0 25 0 19 6 16 6 Trays, japanned tea, 30 inches each 4 6 3 0 2 0 1 5 Vices for blacksmiths cwt 30 0 28 0 22 0 19 6 Wire, brass lb. 1 10 1 4 1 0 0 9 —, iron, No. 6 bund. 16 0 13 0 9 0 7 0 202. I have taken some pains to assure myself of the accuracy of the above table: at different periods of the years quoted the prices may have varied; but I believe it may be considered as a fair approximation. In the course of my enquiries I have been favoured with another list, in which many of the same articles occur, but in this last instance the prices quoted are separated by an interval of twenty years. It is extracted from the books of a highly respectable house at Birmingham; and the prices confirm the accuracy of the former table, so far as they relate to the articles which are found in that list. Prices of 1812 and 1832 Reduction per cent in price of Description 1812 1832 1812 s. d. s. d. Anvils cwt 25 0 14 0 44 Awls, Liverpool blades gross 3 6 1 0 71 Candlesticks, iron, plain 3 103/4 2 31/2 41 screwed 6 41/2 3 9 41 Bed screws, 6 inch square head gross 7 6 4 6 40 flat head gross 8 6 4 8 45 Curry-combs, 6 barred dozen 4 01/2 1 0 75 Reduction per cent in price of Description 1812 1832 1812 s. d. s. d. Curry-combs, 8 barred dozen 5 51/2 1 5 74 patent, 6 barred dozen 7 11/2 1 5 80 8 barred dozen 8 63/4 1 10 79 Fire-irons, iron head, No. 1. 1 41/2 0 73/4 53 No. 2 1 6 0 81/2 53 No. 3 1 81/4 0 91/2 53 No. 4 1 101/2 0 101/2 53 Gun-locks, single roller each 7 21/2 1 11 73 Locks, 1 1/4 brass, port. pad 16 0 2 6 85 2 1/2 inch 3 keyed till-locks each 2 2 0 9 65 Shoe tacks gross 5 0 2 0 60 Spoons, tinned, iron table gross 22 6 7 0 69 Stirrups. com. tinned, 2 bar dozen 7 0 2 9 61 Trace-chains, iron cwt 46 91/2 15 0 68 Prices of the principal materials, used in mines in Cornwall, at different periods [I am indebited to Mr John Taylor for this interesting table] ALL DELIVERED AT THE MINES Description 1800 1810 1820 1830 1832 s. d. s. d. s. d. s. d. s. d. Coals wey 81 7 85 5 53 4 51 0 40 0 Timber (balk) foot 2 0 4 0 1 5 1 0 0 10 (oak) foot 3 31/2 3 0 3 6 3 3 Ropes cwt 66 0 84 0 48 6 40 0 40 0 Iron (common bar) cwt 20 6 14 6 11 0 7 0 6 6 Common castings cwt 16 0 15 0 8 0 6 6 Pumps cwt 16s. & 17s. 17s. & 18s. 12s. & 15s. 6 6 6 10 Gunpowder 100 lbs. 114 2 117 6 68 0 52 6 49 0 Candles 9 3 10 0 8 9 5 11 4 10 Tallow cwt 72 0 84 0 65 8 52 6 43 0 Leather lb. 2 4 2 3 24 22 21 Blistered steel cwt 50 0 44 0 38 0 2s. nails cwt 32 0 28 6 22 0 17 0 16 6 203. I cannot omit availing myself of this opportunity of calling the attention of the manufacturers, merchants, and factors, in all our manufacturing and commercial towns, to the great importance, both for their own interests, and for that of the population to which their capital gives employment, of collecting with care such averages from the actual sales registered in their books. Nor, perhaps, would it be without its use to suggest, that such averages would be still more valuable if collected from as many different quarters as possible; that the quantity of the goods from which they are deduced, together with the greatest deviations from the mean, ought to be given; and that if a small committee were to undertake the task, it would give great additional weight to the information. Political economists have been reproached with too small a use of facts, and too large an employment of theory. If facts are wanting, let it be remembered that the closet-philosopher is unfortunately too little acquainted with the admirable arrangements of the factory, and that no class of persons can supply so readily, and with so little sacrifice of time, the data on which all the reasonings of political economists are founded, as the merchant and manufacturer; and, unquestionably, to no class are the deductions to which they give rise so important. Nor let it be feared that erroneous deductions may be made from such recorded facts: the errors which arise from the absence of facts are far more numerous and more durable than those which result from unsound reasoning respecting true data. 204. The great diminution in price of the articles here enumerated may have arisen from several causes: 1. The alteration in the value of the currency. 2. The increased value of gold in consequence of the increased demand for coin. The first of these causes may have had some influence, and the second may have had a very small effect upon the two first quotations of prices, but none at all upon the two latter ones. 3. The diminished rate of profit produced by capital however employed. This may be estimated by the average price of three per cents at the periods stated. 4. The diminished price of the raw materials out of which these articles were manufactured. The raw material is principally brass and iron, and the reduction upon it may, in some measure, be estimated by the diminished price of iron and brass wire, in the cost of which articles, the labour bears a less proportion than it does in many of the others. 5. The smaller quantity of raw material employed, and perhaps, in some instances, an inferior, quality of workmanship. 6. The improved means by which the same effect was produced by diminished labour. 205. In order to afford the means of estimating the influence of these several causes, the following table is subjoined: 1812 1818 1824 1828 1830 1832 Average Price of L s d. L s. d. L s d L s. d L s d L s. d Gold. per oz 4 15 6 4 0 3 17 61/2 3 17 7 3 17 91/2 3 17 10 1/2 Value of currency. per cent 79 5 3 97 6 10 100 100 100 100 Price of 3 per cent consols 591/4 781/4 935/8 86 893/4 821/2 Wheat per quarter 6 5 0 4 1 0 3 2 l 3 1 1 10 3 14 6 2 19 3 English pig iron at Birmingham 7 l0 0 6 7 6 6 l0 0 5 10 0 4 l0 0 English bar iron at Birmingham 10 10 0 9 10 0 7 15 0 6 0 0 5 0 0 Swedish bar iron in London, excluding duty of from L4 to L6 10s per ton 16 10 0 17 10 0 14 0 0 14 10 0 13 15 0 13 2 0 As this table, if unaccompanied by any explanation, might possibly lead to erroneous conclusions, I subjoin the following observations, for which I am indebted to the kindness of Mr Tooke, who may yet, I hope, be induced to continue his valuable work on High and Low Prices, through the important period which has elapsed since its publication. 'The table commences with 1812, and exhibits a great falling off in the price of wheat and iron coincidently with a fall in the price of gold, and leading to the inference of cause and effect. Now, as regards wheat, it so happened that in 1812 it reached its highest price in consequence of a series of bad harvests, when relief by importation was difficult and enormously expensive. In December, 1813, whilst the price of gold had risen to L5, the price of wheat had fallen to 73s., or 50 per cent under what it had been in the spring of 1812; proving clearly that the two articles were under the influence of opposite causes. 'Again, in 1812, the freight and insurance on Swedish iron were so much higher than at present as to account for nearly the whole of the difference of price: and in 1818 there had been an extensive speculation which had raised the price of all iron, so that a part of the subsequent decline was a mere reaction from a previously unfounded elevation. More recently, in 1825, there was a great speculative rise in the article, which served as a strong stimulus to increased production: this, aided by improved power of machinery, has proceeded to such an extent as fully to account for the fall of price.' To these reflections I will only add, that the result of my own observation leads me to believe that by far the most influential of these causes has been the invention of cheaper modes of manufacturing. The extent to which this can be carried, while a profit can yet be realized at the reduced price, is truly astonishing, as the following fact, which rests on good authority, will prove. Twenty years since, a brass knob for the locks of doors was made at Birmingham; the price, at that time, being 13s. 4d. per dozen. The same article is now manufactured, having the same weight of metal, and an equal, or in fact a slightly superior finish, at 1s. 9 1/4d. per dozen. One circumstance which has produced this economy in the manufacture is, that the lathe on which these knobs are finished is now turned by a steam-engine; so that the workman, relieved from that labour, can make them twenty times as fast as he did formerly. 206. The difference of price of the same article, when of various dimensions at different periods in the same country—and in different countries—is curiously contrasted in the annexed table. Comparative price of plate glass, at the manufactories of London, Paris, Berlin, and Petersburg DIMENSIONS LONDON PARIS BERLIN PETERSBURG Height Breadth 1771 1794 1832 1825 1835 1828 1825 in inches in inches L s d L s d L s d L s d L s d L s d L s d 16 16 0103 0101 0176 087 076 081 0410 30 20 146 232 2610 11610 1710 0106 1210 50 30 24 2 4 11 5 0 6 12 10 9 0 5 5 0 3 8 13 0 5 15 0 60 40 67 14 10 27 0 0 13 9 6 22 7 5 10 4 3 21 18 0 12 9 0 76 40 43 6 0 19 2 9 36 4 5 14 17 5 35 2 11 17 5 0 90 50 84 8 0 34 12 9 71 3 8 28 13 4 33 18 7 100 75 275 0 0 74 5 10 210 13 3 70 9 7 120 75 97 15 9 354 3 2 98 3 10 The price of silvering these plates is twenty per cent on the cost price for English glass; ten per cent on the cost price for Paris plates; and twelve and a half on those of Berlin. The following table shews the dimensions and price, when silvered, of the largest plates of glass ever made by the British Plate Glass Company, which are now at their warehouse in London: Height Breadth Price when silvered Inches Inches L s. d. 132 84 200 8 0 146 81 220 7 0 149 84 239 1 6 131 83 239 10 7 160 80 246 15 4 The prices of the largest glass in the Paris lists when silvered, and reduced to English measure, were: Year Inches Inches Price when silvered L s. d. 1825 128 80 629 12 0 1835 128 80 136 19 0 207. If we wish to compare the value of any article at different periods of time, it is clear that neither any one substance, nor even the combination of all manufactured goods, can furnish us with an invariable unit by which to form our scale of estimation. Mr Malthus has proposed for this purpose to consider a day's labour of an agricultural labourer, as the unit to which all value should be referred. Thus, if we wish to compare the value of twenty yards of broad cloth in Saxony at the present time, with that of the same kind and quantity of cloth fabricated in England two centuries ago, we must find the number of days' labour the cloth would have purchased in England at the time mentioned, and compare it with the number of days' labour which the same quantity of cloth will now purchase in Saxony. Agricultural labour appears to have been selected, because it exists in all countries, and employs a large number of persons, and also because it requires a very small degree of previous instruction. It seems, in fact, to be merely the exertion of a man's physical force; and its value above that of a machine of equal power arises from its portability, and from the facility of directing its efforts to arbitrary and continually fluctuating purposes. It may perhaps be worthy of enquiry, whether a more constant average might not be deduced from combining with this species of labour those trades which require but a moderate exertion of skill and which likewise exist in all civilized countries, such as those of the blacksmith and carpenter, etc.(1*) In all such comparisons there is, however, another element, which, though not essentially necessary, will yet add much to our means of judging. It is an estimate of the quantity of that food on which the labourer usually subsists, which is necessary for his daily support, compared with the quantity which his daily wages will purchase. 208. The existence of a class of middlemen, between small producers and merchants, is frequently advantageous to both parties; and there are certain periods in the history of several manufactures which naturally call that class of traders into existence. There are also times when the advantage ceasing, the custom of employing them also terminates; the middlemen, especially when numerous, as they sometimes are in retail trades, enhancing the price without equivalent good. Thus, in the recent examination by the House of Commons into the state of the coal trade, it appears that five-sixths of the London public is supplied by a class of middlemen who are called in the trade Brass plate coal merchants: these consist principally of merchants' clerks, gentlemen's servants, and others, who have no wharfs of their own, but merely give their orders to some true coal merchant, who sends in the coals from his wharf: the brass plate coal merchants, of course, receiving a commission for his agency. 209. In Italy this system is carried to a great extent amongst the voituriers, or persons who undertake to convey travellers. There are some possessed of greater fluency and a more persuasive manner who frequent the inns where the English resort, and who, as soon as they have made a bargain for the conveyance of a traveller, go out amongst their countrymen and procure some other voiturier to do the job for a considerably smaller sum, themselves pocketing the difference. A short time before the day of starting, the contractor appears before his customer in great distress, regretting his inability to perform the journey on account of the dangerous illness of a mother or some relative, and requesting to have his cousin or brother substituted for him. The English traveller rarely fails to acquiesce in this change, and often praises the filial piety of the rogue who has deceived him. NOTES: 1. Much information for such an enquiry is to be found, for the particular period to which it refers, in the Report of the Committee of the House of Commons on Manufacturers' Employment, 2 July, 1830. 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. Charles Babbage (2003). On the Economy of Machinery and Manufactures. Urbana, Illinois: Project Gutenberg. Retrieved https://www.gutenberg.org/cache/epub/4238/pg4238.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

Of Price as Measured by Money

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 . CAOUTCHOUC. here CAOUTCHOUC. A. Levy contributes the following brief account of this subject to the : Moniteur Scientifique The crude gum cut in irregular strips is passed five or six times between two strong rolls sixteen inches in diameter, and making two or three revolutions per minute. These rolls are kept wet by water trickling on them. This broad strip of gum is perforated with foreign substances and looks like a sieve. It is next put in the cutting machine, a horizontal drum provided with an axle having knives on it. So much heat is produced by this cutting that the water would soon boil if it were not renewed. A second machine of this kind completes the cutting and subdividing, and expels the air and water from it. The mass is then pressed in round or quadrangular blocks. The vulcanization of thin articles from one twenty-fifth to one-sixteenth inch thick, is done by Parkes' patented process, that is, dipping it in carbon disulphide for a short time, to which chloride or bromide of sulphur has been added, and when the solvent has evaporated the sulphur remains behind. Balls, ornamental articles, and surgical apparatus are dipped into melted sulphur at 275° or 300° Fahr. The third most important process consists in mixing in the sulphur mechanically with the gum in the cutting machine. After the pieces have received the form they are to have they are heated with steam or hot air to 275°. Flat articles are vulcanized between press plates heated by steam. This vulcanization is said to have been discovered accidentally by searching different colored stuffs, some of which were dyed yellow with sulphur; the latter stood well. Hard rubber contains more sulphur, and is heated longer and higher. Small or fine tubes and hose are made by a continuous machine that presses it through a hole with a core to it. Large hose is made by wrapping strips around iron rods or tubes. The little air balloons are made in Paris (their value is $300,000) by Brissonet from English Mackintosh cloth. Powdered soapstone is strewed over it in cutting. The edges are united by hammering on a horn anvil, or by machinery through simple adhesion, and the cut surfaces are smooth. 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

Levy contributes the following brief account of this subject 

On the Economy of Machinery and Manufactures by Charles Babbage is part of the HackerNoon Books Series. You can jump to any chapter in this book . Increase and Diminution of Velocity here Chapter 4. Increase and Diminution of Velocity 32. The fatigue produced on the muscles of the human frame does not altogether depend on the actual force employed in each effort, but partly on the frequency with which it is exerted. The exertion necessary to accomplish every operation consists of two parts: one of these is the expenditure of force which is necessary to drive the tool or instrument; and the other is the effort required for the motion of some limb of the animal producing the action. In driving a nail into a piece of wood, one of these is lifting the hammer, and propelling its head against the nail; the other is, raising the arm itself, and moving it in order to use the hammer. If the weight of the hammer is considerable, the former part will cause the greatest portion of the exertion. If the hammer is light, the exertion of raising the arm will produce the greatest part of the fatigue. It does therefore happen, that operations requiring very trifling force, if frequently repeated, will tire more effectually than more laborious work. There is also a degree of rapidity beyond which the action of the muscles cannot be pressed. 33. The most advantageous load for a porter who carries wood up stairs on his shoulders, has been investigated by M. Coulomb; but he found from experiment that a man walking up stairs without any load, and raising his burden by means of his own weight in descending, could do as much work in one day, as four men employed in the ordinary way with the most favourable load. 34. The proportion between the velocity with which men or animals move, and the weights they carry, is a matter of considerable importance, particularly in military affairs. It is also of great importance for the economy of labour, to adjust the weight of that part of the animal's body which is moved, the weight of the tool it urges, and the frequency of repetition of these efforts, so as to produce the greatest effect. An instance of the saving of time by making the same motion of the arm execute two operations instead of one, occurs in the simple art of making the tags of bootlaces: these tags are formed out of very thin, tinned, sheet-iron, and were formerly cut out of long strips of that material into pieces of such a breadth that when bent round they just enclosed the lace. Two pieces of steel have recently been fixed to the side of the shears, by which each piece of tinned-iron as soon as it is cut is bent into a semi-cylindrical form. The additional power required for this operation is almost imperceptible, and it is executed by the same motion of the arm which produces the cut. The work is usually performed by women and children; and with the improved tool more than three times the quantity of tags is produced in a given time.(1*) 35. Whenever the work is itself light, it becomes necessary, in order to economize time, to increase the velocity. Twisting the fibres of wool by the fingers would be a most tedious operation: in the common spinning-wheel the velocity of the foot is moderate, but by a very simple contrivance that of the thread is most rapid. A piece of catgut passing round a large wheel, and then round a small spindle, effects this change. This contrivance is common to a multitude of machines, some of them very simple. In large shops for the retail of ribands, it is necessary at short intervals to 'take stock', that is, to measure and rewind every piece of riband, an operation which, even with this mode of shortening it, is sufficiently tiresome, but without it would be almost impossible from its expense. The small balls of sewing cotton, so cheap and so beautifully wound, are formed by a machine on the same principle, and but a few steps more complicated. 36. In turning from the smaller instruments in frequent use to the larger and more important machines, the economy arising from the increase of velocity becomes more striking. In converting cast into wrought-iron, a mass of metal, of about a hundredweight, is heated almost to white heat, and placed under a heavy hammer moved by water or steam power. This is raised by a projection on a revolving axis; and if the hammer derived its momentum only from the space through which it fell, it would require a considerably greater time to give a blow. But as it is important that the softened mass of red-hot iron should receive as many blows as possible before it cools, the form of the cam or projection on the axis is such, that the hammer, instead of being lifted to a small height, is thrown up with a jerk, and almost the instant after it strikes against a large beam, which acts as a powerful spring, and drives it down on the iron with such velocity that by these means about double the number of strokes can be made in a given time. In the smaller tilt-hammers, this is carried still further by striking the tail of the tilt-hammer forcibly against a small steel anvil, it rebounds with such velocity, that from three to five hundred strokes are made in a minute. In the manufacture of anchors, an art in which a similar contrivance is of still greater importance, it has only been recently applied. 37. In the manufacture of scythes, the length of the blade renders it necessary that the workman should move readily, so as to bring every part of it on the anvil in quick succession. This is effected by placing him in a seat suspended by ropes from the ceiling: so that he is enabled, with little bodily exertion, to vary his distance, by pressing his feet against the block which supports the anvil, or against the floor. 38. An increase of velocity is sometimes necessary to render operations possible: thus a person may skate with great rapidity over ice which would not support his weight if he moved over it more slowly. This arises from the fact, that time is requisite for producing the fracture of the ice: as soon as the weight of the skater begins to act on any point, the ice, supported by the water, bends slowly under him; but if the skater's velocity is considerable, he has passed off from the spot which was loaded before the bending has reached the point which would cause the ice to break. 39. An effect not very different from this might take place if very great velocity were communicated to boats. Let us suppose a flatbottomed boat, whose bow forms an inclined plane with the bottom, at rest in still water. If we imagine some very great force suddenly to propel this boat, the inclination of the plane at the forepart would cause it to rise in the water; and if the force were excessive, it might even rise out of the water, and advance, by a series of leaps, like a piece of slate or an oyster shell, thrown as a 'duck and drake'. If the force were not sufficient to pull the boat out of the water, but were just enough to bring its bottom to the surface, it would be carried along with a kind of gliding motion with great rapidity; for at every point of its course it would require a certain time before, it could sink to its usual draft of water; but before that time had elapsed, it would have advanced to another point, and consequently have been raised by the reaction of the water on the inclined plane at its forepart. 40. The same fact, that bodies moving with great velocity have not time to exert the full effect of their weight, seems to explain a circumstance which appears to be very unaccountable. It sometimes happens that when foot-passengers are knocked down by carriages, the wheels pass over them with scarcely any injury, though, if the weight of the carriage had rested on their body, even for a few seconds, it would have crushed them to death. If the view above taken is correct, the injury in such circumstances will chiefly happen to that part of the body which is struck by the advancing wheel. 41. An operation in which rapidity is of essential importance is in bringing the produce of mines up to the surface. The shafts through which the produce is raised are sunk at a very great expense, and it is, of course, desirable to sink as few of them as possible. The matter to be extracted is therefore raised by steam-engines with considerable velocity, and without this many of our mines could not be worked with profit. 42. The effect of great velocity in modifying the form of a cohesive substance is beautifully shown in the process for making window glass, termed "flashing", which is one of the most striking operations in our domestic arts. A workman having dipped his iron tube into the glass pot, and loaded it with several pounds of the melted "metal", blows out a large globe, which is connected with his rod by a short thick hollow neck. Another workman now fixes to the globe immediately opposite to its neck, an iron rod, the extremity of which has been dipped in the melted glass; and when this is firmly attached, a few drops of water separate the neck of the globe from the iron tube. The rod with the globe attached to it is now held at the mouth of a glowing furnace: and by turning the rod the globe is made to revolve slowly, so as to be uniformly exposed to the heat: the first effect of this softening is to make the glass contract upon itself and to enlarge the opening of the neck. As the softening proceeds, the globe is turned more quickly on its axis, and when very soft and almost incandescent, it is removed from the fire, and the velocity of rotation being still continually increased, the opening enlarges from the effect of the centrifugal force, at first gradually, until at last the mouth suddenly expands or "flashes" out into one large circular sheet of red hot glass. The neck of the original globe, which is to become the outer part of the sheet, is left thick to admit of this expansion, and forms the edge of the circular plate of glass, which is called a "Table". The centre presents the appearance of a thick boss or prominence, called the "Bull's-eye", at the part by which it was attached to the iron rod. 43. The most frequent reason for employing contrivances for diminishing velocity, arises from the necessity of overcoming great resistances with small power. Systems of pulleys, the crane, and many other illustrations, might also be adduced here as examples; but they belong more appropriately to some of the other causes which we have assigned for the advantages of machinery. The common smoke-jack is an instrument in which the velocity communicated is too great for the purpose required, and it is transmitted through wheels which reduce it to a more moderate rate. 44. Telegraphs are machines for conveying information over extensive lines with great rapidity. They have generally been established for the purposes of transmitting information during war, but the increasing wants of man will probably soon render them subservient to more peaceful objects. A few years since the telegraph conveyed to Paris information of the discovery of a comet, by M. Gambart, at Marseilles: the message arrived during a sitting of the French Board of Longitude, and was sent in a note from the Minister of the Interior to Laplace, the President, who received it whilst the writer of these lines was sitting by his side. The object in this instance was, to give the earliest publicity to the fact, and to assure to M. Gambart the title of its first discoverer. At Liverpool a system of signals is established for the purposes of commerce, so that each merchant can communicate with his own vessel long before she arrives in the port. NOTES: 1. See Transactions of the Society of Arts, 1826. 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. Charles Babbage (2003). On the Economy of Machinery and Manufactures. Urbana, Illinois: Project Gutenberg. Retrieved https://www.gutenberg.org/cache/epub/4238/pg4238.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

Increase and Diminution of Velocity

On the Economy of Machinery and Manufactures by Charles Babbage is part of the HackerNoon Books Series. You can jump to any chapter in this book . Accumulating Power here Chapter 2. Accumulating Power 20. Whenever the work to be done requires more force for its execution than can be generated in the time necessary for its completion, recourse must be had to some mechanical method of preserving and condensing a part of the power exerted previously to the commencement of the process. This is most frequently accomplished by a fly-wheel, which is in fact nothing more than a wheel having a very heavy rim, so that the greater part of its weight is near the circumference. It requires great power applied for some time to put this into rapid motion; but when moving with considerable velocity, the effects are exceedingly powerful, if its force be concentrated upon a small object. In some of the iron works where the power of the steam-engine is a little too small for the rollers which it drives, it is usual to set the engine at work a short time before the red-hot iron is ready to be removed from the furnace to the rollers, and to allow it to work with great rapidity until the fly has acquired a velocity rather alarming to those unused to such establishments. On passing the softened mass of iron through the first groove, the engine receives a great and very perceptible check; and its speed is diminished at the next and at each succeeding passage, until the iron bar is reduced to such a size that the ordinary power of the engine is sufficient to roll it. 21. The powerful effect of a large flywheel when its force can be concentrated on a point, was curiously illustrated at one of the largest of our manufactories. The proprietor was shewing to a friend the method of punching holes in iron plates for the boilers of steam-engines. He held in his hand a piece of sheet-iron three-eighths of an inch thick, which he placed under the punch. Observing, after several holes had been made, that the punch made its perforations more and more slowly, he called to the engine-man to know what made the engine work so sluggishly, when it was found that the flywheel and punching apparatus had been detached from the steam-engine just at the commencement of his experiment. 22. Another mode of accumulating power arises from lifting a weight and then allowing it to fall. A man, even with a heavy hammer, might strike repeated blows upon the head of a pile without producing any effect. But if he raises a much heavier hammer to a much greater height, its fall, though far less frequently repeated, will produce the desired effect. When a small blow is given to a large mass of matter, as to a pile, the imperfect elasticity of the material causes a small loss of momentum in the transmission of the motion from each particle to the succeeding one; and, therefore, it may happen that the whole force communicated shall be destroyed before it reaches the opposite extremity. 23. The power accumulated within a small space by gunpowder is well known; and, though not strictly an illustration of the subject discussed in this chapter, some of its effects, under peculiar circumstances, are so singular, that an attempt to explain them may perhaps be excused. If a gun is loaded with ball it will not kick so much as when loaded with small shot; and amongst different kinds of shot, that which is the smallest, causes the greatest recoil against the shoulder. A gun loaded with a quantity of sand, equal in weight to a charge of snipe-shot, kicks still more. If, in loading, a space is left between the wadding and the charge, the gun either recoils violently, or bursts. If the muzzle of a gun has accidentally been stuck into the ground, so as to be stopped up with clay, or even with snow, or if it be fired with its muzzle plunged into water, the almost certain result is that it bursts. The ultimate cause of these apparently inconsistent effects is, that every force requires time to produce its effect; and if the time requisite for the elastic vapour within to force out the sides of the barrel, is less than that in which the condensation of the air near the wadding is conveyed in sufficient force to drive the impediment from the muzzle, then the barrel must burst. If sometimes happens that these two forces are so nearly balanced that the barrel only swells; the obstacle giving way before the gun is actually burst. The correctness of this explanation will appear by tracing step by step the circumstances which arise on discharging a gun loaded with powder confined by a cylindrical piece of wadding, and having its muzzle filled with clay, or some other substance having a moderate degree of resistance. In this case the first effect of the explosion is to produce an enormous pressure on everything confining it, and to advance the wadding through a very small space. Here let us consider it as at rest for a moment, and examine its condition. The portion of air in immediate contact with the wadding is condensed; and if the wadding were to remain at rest, the air throughout the tube would soon acquire a uniform density. But this would require a small interval of time; for the condensation next the wadding would travel with the velocity of sound to the other end, from whence, being reflected back, a series of waves would be generated, which, aided by the friction of the tube, would ultimately destroy the motion. But until the first wave reaches the impediment at the muzzle, the air can exert no pressure against it. Now if the velocity communicated to the wadding is very much greater than that of sound, the condensation of the air immediately in advance of it may be very great before the resistance transmitted to the muzzle is at all considerable; in which case the mutual repulsion of the particles of air so compressed, will offer an absolute barrier to the advance of the wadding.(1*) If this explanation be correct, the additional recoil, when a gun is loaded with small shot or sand, may arise in some measure from the condensation of the air contained between their particles; but chiefly from the velocity communicated by the explosion to those particles of the substances in immediate contact with the powder being greater than that with which a wave can be transmitted through them. It also affords a reason for the success of a method of blasting rocks by filling the upper part of the hole above the powder with sand, instead of clay rammed hard. That the destruction of the gun barrel does not arise from the property possessed by fluids, and in some measure also by sand and small shot, of pressing equally in all directions, and thus exerting a force against a large portion of the interior surface, seems to be proved by a circumstance mentioned by Le Vaillant and other travellers, that, for the purpose of taking birds without injuring their plumage, they filled the barrel of their fowling pieces with water, instead of loading them with a charge of shot. 24. The same reasoning explains a curious phenomenon which occurs in firing a still more powerfully explosive substance. If we put a small quantity of fulminating silver upon the face of an anvil, and strike it slightly with a hammer, it explodes; but instead of breaking either the hammer or the anvil, it is found that that part of the face of each in contact with the fulminating silver is damaged. In this case the velocity communicated by the elastic matter disengaged may be greater than the velocity of a wave traversing steel; so that the particles at the surface are driven by the explosion so near to those next adjacent, that when the compelling force is removed, the repulsion of the particles within the mass drives back those nearer to the surface, with such force, that they pass beyond the limits of attraction, and are separated in the shape of powder. 25. i) The success of the experiment of firing a tallow candle through a deal board, would be explained in the same manner, by supposing the velocity of a wave propagated through deal to be greater than that of a wave passing through tallow. 25. ii) The boiler of a steam-engine sometimes bursts even during the escape of steam through the safety-valve. If the water in the boiler is thrown upon any part which happens to be red hot, the steam formed in the immediate neighbourhood of that part expands with greater velocity than that with which a wave can be transmitted through the less heated steam; consequently one particle is urged against the next, and an almost invincible obstacle is formed, in the same manner as described in the case of the discharge of a gun. If the safety-valve is closed, it may retain the pressure thus created for a short time, and even when it is open the escape may not be sufficiently rapid to remove all impediment; there may therefore exist momentarily within the boiler pressures of various force, varying from that which can just lift the safety-valve up to that which is sufficient, if exerted during an extremely small space of time, to tear open the boiler itself. 26. This reasoning ought, however, to be admitted with caution; and perhaps some inducement to examine it carefully may be presented by tracing it to extreme cases. It would seem, but this is not a necessary consequence, that a gun might be made so long, that it would burst although no obstacle filled up its muzzle. It should also follow that if, after the gun is charged, the air were extracted from the barrel, though the muzzle be then left closed, the gun ought not to burst. It would also seem to follow from the principle of the explanation, that a body might be projected in air, or other elastic resisting medium, with such force that, after advancing a very short space it should return in the same direction in which it was projected. NOTES: 1. See Poisson's remarks, Ecole Polytec. Cahier, xxi, p. 191. 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. Charles Babbage (2003). On the Economy of Machinery and Manufactures. Urbana, Illinois: Project Gutenberg. Retrieved https://www.gutenberg.org/cache/epub/4238/pg4238.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

Accumulating Power

How it Works by Archibald Williams is part of the HackerNoon Books Series. You can jump to any chapter in this book . WIRELESS TELEGRAPHY. here Chapter VII. WIRELESS TELEGRAPHY. The transmitting apparatus—The receiving apparatus—Syntonic transmission—The advance of wireless telegraphy. IN our last chapter we reviewed briefly some systems of sending telegraphic messages from one point of the earth's surface to another through a circuit consisting partly of an insulated wire and partly of the earth itself. The metallic portion of a long circuit, especially if it be a submarine cable, is costly to install, so that in quite the early days of telegraphy efforts were made to use the ether in the place of wire as one conductor. When a hammer strikes an anvil the air around is violently disturbed. This disturbance spreads through the molecules of the air in much the same way as ripples spread from the splash of a stone thrown into a pond. When the sound waves reach the ear they agitate the tympanum, or drum membrane, and we "hear a noise." The hammer is here the transmitter, the air the conductor, the ear the receiver. In wireless telegraphy we use the ether as the conductor of electrical disturbances. Marconi, Slaby, Branly, Lodge, De Forest, Popoff, and others have invented apparatus for causing disturbances of the requisite kind, and for detecting their presence. The main features of a wireless telegraphy outfit are shown in Figs. 59 and 61. THE TRANSMITTER APPARATUS. We will first consider the transmitting outfit (Fig. 59). It includes a battery, dispatching key, and an induction coil having its secondary circuit terminals connected with two wires, the one leading to an earth-plate, the other carried aloft on poles or suspended from a kite. In the large station at Poldhu, Cornwall, for transatlantic signalling, there are special wooden towers 215 feet high, between which the aërial wires hang. At their upper and lower ends respectively the earth and aërial wires terminate in brass balls separated by a gap. When the operator depresses the key the induction coil charges these balls and the wires attached thereto with high-tension electricity. As soon as the quantity collected exceeds the resistance of the air-gap, a discharge takes place between the balls, and the ether round the aërial wire is violently disturbed, and waves of electrical energy are propagated through it. The rapidity with which the discharges follow one another, and their travelling power, depends on the strength of the induction coil, the length of the air-gap, and the capacity of the wires. RECEIVING APPARATUS. The human body is quite insensitive to these etheric waves. We cannot feel, hear, or see them. But at the receiving station there is what may be called an "electric eye." Technically it is named a . A Marconi coherer is seen in Fig. 60. Inside a small glass tube exhausted of air are two silver plugs, p p, carrying terminals, t t, projecting through the glass at both ends. A small gap separates the plugs at the centre, and this gap is partly filled with nickel-silver powder. If the terminals of the coherer are attached to those of a battery, practically no current will pass under ordinary conditions, as the particles of nickel-silver touch each other very lightly and make a "bad contact." But if the coherer is also attached to wires leading into the earth and air, and ether waves strike those wires, at every impact the particles will cohere—that is, pack tightly together—and allow battery current to pass. The property of cohesion of small conductive bodies when influenced by Hertzian waves was first noticed in 1874 by Professor D.E. Hughes while experimenting with a telephone. coherer We are now in a position to examine the apparatus of which a coherer forms part (Fig. 61). First, we notice the aërial and earth wires, to which are attached other wires from battery a. This battery circuit passes round the relay magnet r and through two choking coils, whose function is to prevent the Hertzian waves entering the battery. The relay, when energized, brings contact d against e and closes the circuit of battery b, which is much more powerful than battery a, and operates the magnet m as well as the , which is practically an electric bell minus the gong. (The tapper circuit is indicated by the dotted lines.) tapper We will suppose the transmitter of a distant station to be at work. The electric waves strike the aërial wire of the receiving station, and cause the coherer to cohere and pass current. The relay is closed, and both tapper and Morse inker begin to work. The tapper keeps striking the coherer and shakes the particles loose after every cohesion. If this were not done the current of a would pass continuously after cohesion had once taken place. When the key of the transmitter is pressed down, the waves follow one another very quickly, and the acquired conductivity of the coherer is only momentarily destroyed by the tap of the hammer. During the impression of a dot by the Morse inker, contact is made and broken repeatedly; but as the armature of the inker is heavy and slow to move it does not vibrate in time with the relay and tapper. Therefore the Morse instrument reproduces in dots and dashes the short and long depressions of the key at the transmitting station, while the tapper works rapidly in time with the relay. The Morse inker is shown diagrammatically. While current passes through m the armature is pulled towards it, the end p, carrying an inked wheel, rises, and a mark is made on the tape w, which is moved continuously being drawn forward off reel r by the clockwork—or electrically-driven rollers r1 r2. SYNTONIC TRANSMISSION. If a number of transmitting stations are sending out messages simultaneously, a jumble of signals would affect all the receivers round, unless some method were employed for rendering a receiver sensitive only to the waves intended to influence it. Also, if distinction were impossible, even with one transmitter in action its message might go to undesired stations. There are various ways of "tuning" receivers and transmitters, but the principle underlying them all is analogous to that of mechanical vibration. If a weight is suspended from the end of a spiral spring, and given an upward blow, it bobs up and down a certain number of times per minute, every movement from start to finish having exactly the same duration as the rest. The resistance of the air and the internal friction of the spring gradually lessen the amplitude of the movements, and the weight finally comes to rest. Suppose that the weight scales 30 lbs., and that it naturally bobs twenty times a minute. If you now take a feather and give it a push every three seconds you can coax it into vigorous motion, assuming that every push catches it exactly on the rebound. The same effect would be produced more slowly if 6 or 9 second intervals were substituted. But if you strike it at 4, 5, or 7 second intervals it will gradually cease to oscillate, as the effect of one blow neutralizes that of another. The same phenomenon is witnessed when two tuning-forks of equal pitch are mounted near one another, and one is struck. The other soon picks up the note. But a fork of unequal pitch would remain dumb. Now, every electrical circuit has a "natural period of oscillation" in which its electric charge vibrates. It is found possible to "tune," or "syntonize," the aërial rod or wire of a receiving station with a transmitter. A vertical wire about 200 feet in length, says Professor J.A. Fleming, has a natural time period of electrical oscillation of about one-millionth of a second. Therefore if waves strike this wire a million times a second they will reinforce one another and influence the coherer; whereas a less or greater frequency will leave it practically unaffected. By adjusting the receiving circuit to the transmitter, or , selective wireless telegraphy becomes possible. vice versâ ADVANCE OF WIRELESS TELEGRAPHY. The history of wireless telegraphy may be summed up as follows:— 1842.—Professor Morse sent aërial messages across the Susquehanna River. A line containing a battery and transmitter was carried on posts along one bank and "earthed" in the river at each end. On the other bank was a second wire attached to a receiver and similarly earthed. Whenever contact was made and broken on the battery side, the receiver on the other was affected. Distance about 1 mile. 1859.—James Bowman Lindsay transmitted messages across the Tay at Glencarse in a somewhat similar way. Distance about ½ mile. 1885.—Sir William Preece signalled from Lavernock Point, near Cardiff, to Steep Holm, an island in the Bristol Channel. Distance about 5½ miles. In all these electrical of current was employed. induction 1886.—Hertzian waves discovered. 1895.—Professor A. Popoff sent Hertzian wave messages over a distance of 3 miles. 1897.—Marconi signalled from the Needles Hotel, Isle of Wight, to Swanage; 17½ miles. 1901.—Messages sent at sea for 380 miles. 1901, Dec. 17.—Messages transmitted from Poldhu, Cornwall, to Hospital Point, Newfoundland; 2,099 miles. Mr. Marconi has so perfected tuning devices that his transatlantic messages do not affect receivers placed on board ships crossing the ocean, unless they are purposely tuned. Atlantic liners now publish daily small newspapers containing the latest news, flashed through space from land stations. In the United States the De Forest and Fessenden systems are being rapidly extended to embrace the most out-of-the-way districts. Every navy of importance has adopted wireless telegraphy, which, as was proved during the Russo-Japanese War, can be of the greatest help in directing operations. 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. Archibald Williams (2009). How it Works. Urbana, Illinois: Project Gutenberg. Retrieved https://www.gutenberg.org/cache/epub/28553/pg28553-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

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