heroes of the telegraph-第22节
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uld steam forwards or backwards with equal ease； it became unnecessary to pass the cable forward before hauling it in； if a fault were discovered in the part submerged： the motion of the ship had only to be reversed； the stern rudder fixed； and the bow rudder turned； while a small engine was employed to haul the cable back over the stern drum； which had been used a few minutes before to pay it out。
The first expedition of the Faraday was the laying of the Direct United States cable in the winter of 1874 a work which； though interrupted by stormy weather； was resumed and completed in the summer of 1875。 She has been engaged in laying several Atlantic cables since； and has been fitted with the electric light； a resource which has proved of the utmost service； not only in facilitating the night operations of paying…out； but in guarding the ship from collision with icebergs in foggy weather off the North American coast。
Mention of the electric light brings us to an important act of the inventor； which； though done on behalf of his brother Werner； was pregnant with great consequences。 This was his announcement before a meeting of the Royal Society； held on February 14； 1867； of the discovery of the principle of reinforcing the field magnetism of magneto…electric generators by part or the whole of the current generated in the revolving armaturea principle which has been applied in the dynamo…electric machines； now so much used for producing electric light and effecting the transmission of power to a distance by means of the electric current。 By a curious coincidence the same principle was enunciated by Sir Charles Wheatstone at the very same meeting； while a few months previously Mr。 S。 A。 Varley had lodged an application for a British patent； in which the same idea was set forth。 The claims of these three inventors to priority in the discovery were； however； anticipated by at least one other investigator； Herr Soren Hjorth； believed to be a Dane by birth； and still remembered by a few living electricians； though forgotten by the scientific world at large； until his neglected specification was unexpectedly dug out of the musty archives of the British Patent Office and brought into the light。
The announcement of Siemens and Wheatstone came at an apter time than Hjorth's； and was more conspicuously made。 Above all； in the affluent and enterprising hands of the brothers Siemens； it was not suffered to lie sterile； and the Siemens dynamo…electric machine was its offspring。 This dynamo； as is well known； differs from those of Gramme and Paccinotti chiefly in the longitudinal winding of the armature； and it is unnecessary to describe it here。 It has been adapted by its inventors to all kinds of electrical work； electrotyping； telegraphy； electric lighting； and the propulsion of vehicles。
The first electric tramway run at Berlin in 1879 was followed by another at Dusseldorf in 1880； and a third at Paris in 1881。 With all of these the name of Werner Siemens was chiefly associated； but William Siemens had also taken up the matter； and established at his country house of Sherwood； near Tunbridge Wells； an arrangement of dynamos and water…wheel； by which the power of a neighbouring stream was made to light the house； cut chaff turn washing…machines； and perform other household duties。 More recently the construction of the electric railway from Portrush to Bushmills； at the Giant's Causeway； engaged his attention； and this； the first work of its kind in the United Kingdom； and to all appearance the pioneer of many similar lines； was one of his very last undertakings。
In the recent development of electric lighting； William Siemens； whose fame had been steadily growing； was a recognised leader； although he himself made no great discoveries therein。 As a public man and a manufacturer of great resources his influence in assisting the introduction of the light has been immense。 The number of Siemens machines and Siemens electric lamps； together with measuring instruments such as the Siemens electro…dynamometer； which has been supplied to different parts of the world by the firm of which he was the head； is very considerable； and probably exceeds that of any other manufacturer； at least in this country。
Employing a staff of skilful assistants to develop many of his ideas； Dr。 Siemens was able to produce a great variety of electrical instruments for measuring and other auxiliary purposes； all of which bear the name of his firm； and have proved exceedingly useful in a practical sense。
Among the most interesting of Siemens's investigations were his experiments on the influence of the electric light in promoting the growth of plants； carried out during the winter of 1880 in the greenhouses of Sherwood。 These experiments showed that plants do not require a period of rest； but continue to grow if light and other necessaries are supplied to them。 Siemens enhanced the daylight； and； as it were； prolonged it through the night by means of arc lamps； with the result of forcing excellent fruit and flowers to their maturity before the natural time in this climate。
While Siemens was testing the chemical and life…promoting influence of the electric arc light； he was also occupied in trying its temperature and heating power with an 'electric furnace；' consisting of a plumbago crucible having two carbon electrodes entering it in such a manner that the voltaic arc could be produced within it。 He succeeded in fusing a variety of refractory metals in a comparatively short time： thus； a pound of broken files was melted in a cold crucible in thirteen minutes； a result which is not surprising when we consider that the temperature of the voltaic arc； as measured by Siemens and Rosetti； is between 2；000 and 3；000 Deg。 Centigrade； or about one…third that of the probable temperature of the sun。 Sir Humphry Davy was the first to observe the extraordinary fusing power of the voltaic arc； but Siemens first applied it to a practical purpose in his electric furnace。
Always ready to turn his inventive genius in any direction； the introduction of the electric light； which had given an impetus to improvement in the methods of utilising gas； led him to design a regenerative gas lamp； which is now employed on a small scale in this country； either for street lighting or in class…rooms and public halls。 In this burner； as in the regenerative furnace； the products of combustion are made to warm up the air and gas which go to feed the flame； and the effect is a full and brilliant light with some economy of fuel。 The use of coal…gas for heating purposes was another subject which he took up with characteristic earnestness； and he advocated for a time the use of gas stoves and fires in preference to those which burn coal； not only on account of their cleanliness and convenience； but on the score of preventing fogs in great cities； by checking the discharge of smoke into the atmosphere。 He designed a regenerative gas and coke fireplace； in which the ingoing air was warmed by heat conducted from the back part of the grate； and by practical trials in his own office； calculated the economy of the system。 The interest in this question； however； died away after the close of the Smoke Abatement Exhibition； and the experiments of Mr。 Aiken； of Edinburgh； showed how futile was the hope that gas fires would prevent fogs altogether。 They might indeed ameliorate the noxious character of a fog by checking the discharge of soot into the atmosphere； but Mr。 Aiken's experiments showed that particles of gas were in themselves capable of condensing the moisture of the air upon them。 The great scheme of Siemens for making London a smokeless city； by manufacturing gas at the coal…pit and leading it in pipes from street to street； would not have rendered it altogether a fogless one； though the coke and gas fires would certainly have reduced the quantity of soot launched into the air。 Siemens's scheme was rejected by a Committee of the House of Lords on the somewhat mistaken ground that if the plan were as profitable as Siemens supposed； it would have been put in practice long ago by private enterprise。
》From the problem of heating a room； the mind of Siemens also passed to the maintenance of solar fires； and occupied itself with the supply of fuel to the sun。 Some physicists have attributed the continuance of solar heat to the contraction of the solar mass； and others to the impact of cometary matter。 Imbued with the idea of regeneration； and seeking in nature for that thrift of power which he； as an inventor； had always aimed at； Siemens suggested a hypothesis on which the sun conserves its heat by a circulation of its fuel in space。 The elements dissociated in the intense heat of the glowing orb rush into the cooler regions of space； and recombine to stream again towards the sun； where the self…same process is renewed。 The hypothesis was a daring one； and evoked a great deal of discussion； to which the author replied with interest； afterwards reprinting the controversy in a volume； ON THE CONSERVATION OF SOLAR ENERGY。 Whether true or notand time will probably decidethe solar hypothesis of Siemens revealed its author in a new light。 Hitherto he had been the ingenious
