M 



TELEGRAPH, ELECTRIC 



TKI.r/iRAPH, ELECTRIC. 



8t 



After the plate* lure been introduced, the compartment* are filled 

 with will, which U moistened with dilute sulphuric .vid (1 itrong iicid 

 to 15 wter>. Thi* arrangement diminishes the risk of leakage, and 

 lessens the amount of evaporation. The acid ha* to be renewed once 

 in ten or fourteen dan, according to the amount of work performed by 

 ^r.iph. In the Electric Telegraph Company'! central otlico at 

 Lothlniry the batteries are contained in two long narrow chambers in 

 the basement of the building. There are upward* of aixty Daniell'* 

 batteries at work : they take rank a* sixes, twelve*, and twenty-fount, 

 according to the number of their elements or plates, the twenty-four* 

 working the longer lines, and the smaller batteries the shorter circuits. 

 A twenty-four, when in full work, requires only a gill of dilute sul- 

 phuric acid per month, and its zinc plate* last three months. Other 

 batteries require 1 Ib. of sulphate of copper per month, with a little 

 milphate of sine or aalt and water. The entire amount of electric 

 ; employed by this company throughout the country is said, on 

 the authority of an article in the ' Quarterly Review ' (1854), to be pro- 

 duced by SuOO twelve plate batteries, or 06,000 cells, which are lined 

 with 1,500,000 square inches of copper, and about the same of zinc. 

 To work these batteries, 6 tons ot acid and 55 tons of sand are 

 required every year. When a distant station-clerk finds by the weak 

 action of his needle* that the battery is not up to its work, he sends 

 word that it require* " refreshment," and it is accordingly served with 

 its gill of sulphuric acid. 



Another form of battery which continue* in action for a consider- 

 able time consist* of plate* of amalgamated zinc and gas coke excited 

 by solid sulphate of mercury moistened with water ; they are arranged 

 in compartments aa in the sand battery. 



Some lines are worked by means of the magneto-electric machine. 

 (MAI.MLTO KLECTHICITT.] The Atlantic cable during a portion of iU 

 brief existence was worked by a secondary current. An electric cable 

 sunk in water U apt to become charged with electricity after the 

 manner of a Leyden jar, and so to resist the passage of the current 

 along its central conducting wire. The idea was, that by using a 

 secondary current it would by it* pulsations displace the charge, and 

 allow the current to be transmitted. Mr. Whitehouse fed hia double 

 imlurtion coils by means of what be calls a " perpetual maintenance 

 battery." This battery consists of large plates of platinized silver, 

 and amalgamated zinc, mounted in cells of gutta percha. There are 

 several platea, both of silver and zinc, in each cell ; but all the 

 zinc plate* rest upon a longitudinal bar of metal at the bottom 

 of the cell, and all the silver plate* hang upon a similar bar at 

 the top of the cell, so that thus there is virtually but a single 

 stretch of silver, and a single stretch of zinc in operation. This 

 arrangement is made because it enables any portion of either silver 

 or rinc to be removed for repair or renewal without stopping for a 

 moment the operation of the battery. As any one lamina becomes 

 imj>erfect, it can be taken out from it* groove, and replaced. Each 

 cell contains two thousand square inches of acting surface, and u 

 charged with the usual mixture of acid and water, and there are ten 

 such cells in the battery. This combination in go powerful that when 

 the broad strips of copper plate which form the polar extensions are 

 brought into contact or separated, brilliant flashes are p* 

 accompanied by a loud crackling sound. The point* of large pliers 

 are made red-hut in five seconds when placed between them, and iron 

 crew* burn with vivid scintillation. These brilliant effect* are, how- 

 ever, produced at the expense of the apparatus ; the metallic surfaces 

 from which they are emitted rapidly burning away during their con- 

 tinuance. In order to alleviate this injurious effect, contact is made 

 and broken, during the transmission of electrical signals, by means of a 

 key presenting a very large surface of metal. A horizontal bar, 

 flattened at the top, turns backward* and forwards pivot-ways, and 

 tilt* its edge* against twenty fiat brass springs resembling in form the 

 keys of a piano-forte, ten being on each side. A constant slight leak 

 of the current is also continuously maintained through a coil of 

 platinum wire placed in water. By this contrivance the injurious force 

 of the spark is pretty well absorbed and destroyed. The cost of main- 

 taining this magnificent battery at work is said not to exceed a shilling 

 per hour. 



But for the reason above stated the voltaic current is by no means a 

 fleet messenger compared with other agents which are at the command 

 of the electrician. Consequently it in not the electric stream generated 

 in this powerful battery which was designed to be actually .-. nt 

 cross the Atlantic on the performance of telegraph service. This 

 primary power U only uaed to call up and stimulate thu energy of a 

 more speedy traveller. The voltaic current, generated in the > 

 in transmitted to induction coils, arranged in pairs, each coil l mg 

 arranged a* in HulnnkorfTi apparatus, a figure of which in given under 

 XAOXETO ELICTKU-ITT, ooL 428. It is the secondary current induced 

 l.y this apparatus wliich it was proposed should perform the work of 

 rushing across the Atlantic. This inde|-ndi nt mvoml.iry current wan 

 therefor* the Irammtimion tvrrmi. and the coil in which it wan produced 

 was properly the frawMisnon r-,,1. The coil* were used in pain, because 

 each one inductively increase* the power of it* Migttmur. and in 

 return has it* own energy inductively increased a* well. The great 

 beating power of the battery-current u rendered harmless by the size 

 awl extent of tin- primary roil through which it in [Mused. If at any 

 time, by accident, the cuireot should find a short course for itself in 



consequence of the silk covering of the wire being injured, the accident 

 is immediately indicated by the rapid rise of the temperature of tin- 

 coil. The transmission-current necessarily gets considerably weakened 

 when it ha* pasted through a distance of 1800 or 1900 mile*. Con- 

 sequently this weakened current was not to be immediately employed 

 to print or record the signals transmitted. The weakened transmission- 

 current was merely caused to open and close the outlet of a fresh 1 

 destined to do the printing or recording labour. The strand of the 

 Atlantic cable was continued into a coil of fine wire, wound about a 

 bar of soft iron. When the transmission-current flowed through the 

 coil, the bar became a temporary magnet, which had the direct 

 it* polarity determined by the nature of the current (positive or 

 negative) sent through the coiL The pole which U north when the 

 transmission-current is positive, become* south when the tranimission- 

 current U negative. Near to the tein|xjrary magnet a permanent 

 magnet was so placed that it could traverse backward* and forward* 

 upon a pivot as it was actuated by the temporary magnet Th< 

 pole of the permanent magnet was attracted by the south pole of the 

 temporary one, and vice vend ; so that as the polarity of the temporary 

 magnet was reversed, the permanent magnet was made to traverse. 

 When it traversed one way, it opened the outlet of the local battery by 

 effecting a contact, and caused it to print ; when it traversed the other 

 way it shut off the current of the local battery, so that it ceased to 

 print 



It was the peculiar advantage of this relay-instrument (as it U called) 

 that the temporary magnet had no other work to <! than to turn the 

 permanent magnet upon its almost frictionless pivot. It had no spring 

 to overcome, such as is more commonly employed in this class ol 

 instruments. The arrangement was so sensitive that the apparatus 

 could be put in action by a fragment of zinc and a sixpence pressed 

 against the tongue. These relays might indeed be ordinarily heard 

 clicking backward* and forwards, and working automatically when the 

 large induction-coils were in operation within a few feet of 

 actually doing a little business on their own account, although not in 

 communication with any current, and transmitting the same signal* 

 and messages as those which were being forwarded through the agency 

 of the induction-coils. As the poles of the induction-coil magnets were 

 reversed, the poles of the relay-magnets were actuated different way*. 

 Mr. \\~hitehouse made the instrument* even more delicate by 

 ing a second permanent magnet, so that it could be made by a 

 adjustment to increase or diminish the attraction acting on the working 

 magnet, either way. When the printing battery was brought int.. 

 operation by the relay, it delivered its message by the agency of one of 

 Professor Morse's printing instruments already described. 



Professor W. Thomson, in commenting on the above arrangement 

 (' Kncyc. Brit.,' art. ' Electric Telegraph'), prefers the voltaic lattery 

 to any other source of electricity "for all great telegraphic work;'" 

 and he expresses his conviction somewhat boldly, we think, that " if 

 no induction coils and no battery power, either positive or exceeding 

 20 cells of Darnell's negative, had ever been applied to the cable since 

 the landing of its ends, imperfect as it then was, it would be now in 

 full work day and night, with no prospect or probability of failure." 



Secondly, as to the /<. In most parts of England the wires, a* 

 from the commencement of the system in this country, are supported 

 on poles at a height of several feet from the ground ; but in a few 

 cases, such aa along the mail-coach road from London to Dover, a sub- 

 terranean arrangement has been adopted : the wires being encased in a 

 wooden trough, and deposited a foot or two beneath the surface of the 

 ground. This arrangement is also adopted in the streets of 1. 

 and of other large towns. It has also been adopted by the English 

 and Irish Magnetic Company, on a great extent of their lines ; and it is 

 that adopted in Prussia, The wires from the central station in London 

 are insulated by being wrapped with cotton thread, and coated with a 

 mixture of tar, resin, and grease, or gutta percha is used in prefr 

 Nine such wires are packed in a half-inch leaden pipe, and four 

 such pipes are packed in an iron pipe about 3 inches in diameter, 

 which pipes are laid under the foot- pavements, and are thus con. 1 

 to the terminal stations of various railways Testing-posts are placed 

 at intervals along the streets, by which any failure can be detect, 

 the locality of the defective wire ascertained at least within the dis- 

 i two post*. The London District Telegraph Company do not 

 bury their wires, but are now engaged in weaving a metallic web over 

 the tops of our houses. 



The exposed conducting wires which nm along tho side of a 

 railway are of galvanised iron, about the sixth of an inch in di;n 

 The higher price of copper prevent* it from U-ing employed, although 

 this metal is a much better conductor of ''An n 



a great length of wire is to be stretched between two distant points, 

 without immediate support, steel wire is sometimes used. The gal- 

 vanised iron wire, in the neighbourhood of large manufacturing towns, 

 is liable to be attacked by the sulphur acids of the amoke, and tho 

 zinc being converted into a soluble Milphate is washed oil' by the rain, 

 and the iron wire becomes quickly corroded. We have i 

 spoken of the earthenware or glass insulators attached to the post*. 

 for supporting the wire. An insulator should ii"t only lie a non- 

 conductor, but it should throw off the rain quickly and completely, 

 otherwise the moisture will form a conductor to the earth; in< !.<!. 

 the dripping of wet from one line to another below it, will sometime* 



