T B L 



1M 



T K I 



the non-observance of this principle : a despatch from I 

 Plymouth .ntclligcn. hav- I 



ing been commenced l>\ I; 



aad then broki n otf t -, loir, which ' the whole 



meaning. 



.!ie message run thus. ' French 



defeated ;e iuterniption of tin would 



liave been of far less consequence. 



Any means of telegraphic communication which de- 

 IH-nds upon the deci; : nbited at a dis- 



tant station is necessarily dependent upon conti 

 weather: but many plans have been contrive! 

 ing t: i such a manner as to he indepeiide- 



of light and of the state of the at . For com- 



munication between the different parts of a house this 

 object may be effected by a mechanical connection, by 

 chains or wires, between two dials with revolving ii 

 or pointers, in such a way that when one pointer is directed 

 to a particular letter or word inscribed upon the dial to 

 which it .1, tlie other may exhibit a similar 



movement. The attention of the servant is engaged pre- 

 viously by ringing a bell ; and when the required signal 

 lias been "made, n spring returns both indexes to their ori- 

 ginal position. Such a plan, though il for 

 domestic purposes, is not adapted for distant communica- 

 tion. Speaking-pipe*, or tubes to convoy the voice from 

 one place to another. vailable for short distances. 

 but their range is too limited for application on an ex- 

 tended scale. One of the early schemes of this character 

 depends upon the principle of water always finding its 

 level ; hut, independent of the difficulty which migb - 

 from the friction of water in a very long pipe of small 

 diameter, such as would he required to connect the ver- 

 tical tubes in which the observations would he made, such 

 a plan involves the nee 'aving all the com- 

 municating stations at or near the same level. Other 

 hydraulic telegraphs depend upon the incompressihility of 

 water or other liquids ; it being proposed to lay down 

 small pipes of any required length, and to indicate dif- 

 ferent signals by pressing more or less upon the surface of 

 the fluid contained in them, which would, it i 

 transmit the motion to the opposite end of the pii>e, where 

 it might be pointed out upon a dial, or in any other con- 

 venient manner. Mr. Vauance described such a method 

 of telegraphic communication in a pamphlet, published in 

 1825, of which Hebert gives some account 

 and Mecfiiui/i'- , vol. ii.. pp. 787-8) ; and 

 some similar schemes liave been more recently pro- 

 pounded. Air confined in small pipes has also been tried 

 to a limited extent as a pneumatic telegraph : but in this. 

 as well as in the hydraulic system, the risk of I 

 serious disadvantage. The application of electricity to 

 telegraphic communication is attended with fewer dif- 

 ficulties, and has rccentU on an 

 important scale by Mc-srs. Wheats: ooke. The 

 possibility of so apph ing it was coneeive-i ,] per- 

 sons long before It was attempted on a piactie:il scale. 

 Arthur Young, who visited Fiance in 17 S '7. 17^. and 

 17*!l. mentions, in his travels, the ex] of M. 

 Lomond, who was able by means of electricity to convey 

 messages from one room to another; and the Rev. Mr. 

 Gamble, in his description of his original shutter-telegraph, 

 allude* to the project of electrical communication. Mr. 

 Fiancis Ronalds, in a pamphlet on this subject, published 

 in 1K23, states thai Cuvallo proposed to convey intel- 

 ligence by passing given numbers of sparks through au 

 insulated wire; ana that, in lHl(j. he had I 

 experiments upon this principle, which ! 

 promising than : 



tricitv, which had nnans 



and Americans. He suee ntting 



II through a length of ciirht in. wire ; 





 adapting the principle to telegraphic cotmnu: 



It is however to the join' 

 and Professor V 



their practical application; and in a 



respecting their relative | <>n with the 



invention, drawn up at their request by Sir M. I. Brunei 

 and I 1 iianiell. it is observed lh:i 



entitled to -land alone, a whom this 



country is indebted for having , durcd and 



carried out the electric telegraph a* a useful undertaking. 



promising to be a worfc of national importance ; and Pro- 

 fewor WneaUtono i< nekn 'tific man 



whose profound and successful ! pre- 



the public to ri ;>nic- 



tieal n]>])lication.' Their ' which wa- 



in 1837, acts upon principles fonndr 

 brated discovery, that a magnetic or compass needle 

 through the agency of a voltaic curie 

 an artificial polarity. [Ei.ECTi<< ., p. 



:U2.] -Tims,' explains Mr. < 

 trays, p. 14), ' as a natural stream of el< 

 round the circumference of the earth c: 

 needles in general to be deflected at right an: 

 course. ;ils the north nn<l south poles, so n'i artifi- 



cam of electricity of adequate strength will cause. 

 magnetic ni ithin its influt- -imi- 



larly deflected at right angles to ... t ) in t 



may be. If then a magnetic n, placed parallel 



and near to any part of a com!; 

 suppose to be" laid down between I.nndon and Hlar 1 

 the transmission of an electric current from a vollai 

 tery would cause the needle to change its portion. 

 to stand during the continuance of the current at ri<:ht 

 angles to the wire, being turned in one direction or thp 

 other according to the course of the current. If th: 

 flexion of the needle were limited by two fixed 

 placed respectively at the two sides of one of its pules, the 

 motion of that pole to one stop might evidently constitute 

 one signal, and its motion to the another signal.' 



Such an apparatus is shown in Fig. 1 1, the dial upon which 

 the signals are represented being removed. In this . 



Fis;. H. 



may be supposed to represent the battery, and b l> the con- 

 ducting wire, which is formed behind the dial into a coil 

 c : dil is the magnet, which is mounted upon an axi- 

 ing through the coil, and carrying upon its extremity, 

 which comes through the dial, an index or poii ' 

 arrows indicate the direction of the current rcqn 

 licet the magnet to the ] .1 in the figure : 



and a eui rent in the opposite dire". 

 deflexion towards the opi . AVhile no current 



- through the v. : 

 vertical. The next i h in- 



Fig. 12. 



strumcnts complete, and connected togetli 



: in tubes, which ni nffth. 



i these maybe . lories, the 



at an inter'medi; n. and the thml at Ii 



wall ; and as each is provided with n battery, and a handle 

 (beneath the dial i by which the conducting wi 

 connected with it nt pleasure, the attendant 

 station at which such an instrument is placed can instan- 

 taneously communicate the signal to stop' or t,, ^ on' 

 to all the other stations: attention I 



by ringing A bell, placed above the dial, by an in- 

 i'lii of the \oltaie current. liv this beau- 

 tifully simp "liar method of working 

 the trairm upon the Blaekwall railway [RAILWAY, vol. xix.. 



