COPYING TELEGRAPH.] UNDULATORY FORCES. ELECTPvO-MAGNETISM. 



207 



travelled from the piano to the needles ; and as each key 

 was pressed down, a mark was imprinted on the cloth 

 by its corresponding needle ; the length of the mark 

 indicating the value of the note such as a quaver, 

 a crotchet, and so on. We have frequently played 

 rapidly-executed music on a piano so fitted, and every 

 note was thus printed as quickly and as accurately as 

 it was performed. When the cloth was removed from 

 the roller, the lines might immediately be read, or 

 transposed into the ordinary form of musical notation. 

 The instrument would be of great value to composers, 

 because every idea, as it found expression on the piano, 

 Ac., would simultaneously be printed by the electric 

 current. We believe that Mr. Whitehouse has not car- 

 ried out his invention beyond making the model we 

 have described. 



BAKEWELL'S COPYING TELEGRAPH. 



PERHAPS the simplest and most interesting instrument 

 constructed on the principles we have explained, is that 

 invented by Mr. Bakewell; by means of which the hand- 

 writing of the sender of the mes- 

 sage is faithfully copied by the 

 electric current, at any distance from 

 the station whence the message is 

 forwarded. This certainly, at first 

 sight, seems beyond belief; but by 

 a little investigation, we shall find 

 that it is only the result of a most 

 ious application of principles, 

 to which we have already very fre- 

 quently drawn attention. The whole 

 secret of the art consists in so ar- 

 ranging a conductor with a partial 

 non-conducting surface, that, by means of the latter, 

 the current of electricity may be intercepted; :m<l 

 this is managed after the following manner : The 

 message is first written, by means of a weak spi- 

 rituous varnish, on a sheet of tinfoil, and it is then 

 dried. It is evident, that if a wire, connected with one 

 plate of a voltaic cell, be drawn over the foil prepared in 

 this manner, whilst the wire from the other plate is at- 

 tached to the foil, the current will be complete, so long 

 as each wire is in contact with the foil ; and it will be 

 broken as soon as the wire, passed over tha foil, touches 

 the varnished surface, because such is, f course, a non- 

 conductor. Now, if the tinfoil be conn-cted, by means 

 of a wire, with such an instrument as wi. have described 

 in a previous page,* so that it may be electrically con- 

 nected with the needle, and one wire of the battery be 

 in contact with the roller of that apparatus the wire 

 from the other plate being passed over the written tin- 

 foil surface no mark will be made on the prepared cloth 

 when the battery wire comes ii contact with the 

 varnish ; but whenever it touches the tinfoil, a blue mark 

 will be printed on the cloth. If the needle, instead of 

 being stationary, is allowed to traverse from one side of 

 the roller to the other, whilst the roller itself is quickly 

 moved round by clockwork, the continuous straight lines 

 will be printed when the circuit is completed ; which, 

 however, will be interspersed with white spaces when- 

 ever the circuit is broken by the interposition of the 

 varnished surface. Supposing the varnished surface to 

 be a straight line across the tinfoil, then the printed 



-O- Fig. 31. 



No. 1, in Fig. 31, represents the tinfoil sheet, a, from 

 which the signal is transmitted, crossed by the varnished 

 line, b, which is the non-conductor ; No. 2, c,. is the 

 cloth in which the signal is received and printed; d 

 being the white space, unmarked with lines, and cor- 

 responding to the varnished surface of the tinfoil plate ; 

 and e e are the blue lines printed by the traversing 

 needle, which receives the electric current from the foil 

 No. 2, in fact, gives a representation of the cloth as it 

 appears when taken off the rollers. 



Now, the principle being established, it does not 

 matter whether the line on the foil be straight, curved, 

 or of any form ; hence, if such be ordinary writing, that 

 would be copied on to the cloth in an exact fac-simile of 

 the original, just as we observe in the copy shown in 

 No. 2. This is just the plan adopted, and the result 

 arrived at, by Mr. Bakewell's arrangement, provided 

 that certain mechanical details are observed, to which 

 we shall presently allude. The following diagram shows 

 the appearance of the original, and printed, copy of a 

 message, as illustrated by Mr. Bakewell, in his work on 

 the subject. 



Fig. 3Z.NO. I. 



So. i. 



No. 2. 



copy wotud present a number of blue lines, crossed by a 

 white one as is shown in the above diagram.' 



See ante, p. 266 J Fig. 30. 



No. 1, Fig. 32, represents the original, with the letters 

 in black on the tinfoil ; and No. 2 is the printed copy, 

 having the letters in white intercepting the line pro- 

 duced by the needle. Our readers will thus perceive, 

 that by this plan, an exact copy of the handwriting of 

 any person may be transmitted by telegraph a fact that 

 makes Mr. Bakewell's invention rank very high as an 

 instance of inventive genius. But, unfortunately, there 

 is a very serious drawback to its utility, which is owing 

 to the necessity that exists for both the transmitting 

 and receiving-rollers to move at the same speed and at 

 the same moment ; and, consequently, through equal 

 spaces in the same period of time. To effect this, Mr. 

 Bakewell introduced regulating apparatus, worked by a'l 

 electro-magnet, so that one roller could only proceed at 

 the same rate as the other. In fact, in such an ar- 

 rangement, the magnet acts in a similar manner to tha 

 pendulum of a clock. It is well known, that the weight 

 or spring of a clock would quickly "run down" were it 

 not for the action which a pendulum exerts on the 

 seconds, or first wheel. A pendulum, thirty-nine inches 

 long, beats about once in a second of time ; and the. 

 spring of the clock is only required to keep up that 

 motion. But two pendula never beat exactly together : 

 thus they would not be effective as regulating arrange- 

 ments in Mr. Bakewell's apparatus. Hence the employ- 

 ment of the electro-magnets, which necessarily act to- 

 gether, because their motion is mutually dependent. 

 We are precluded from illustrating the mechanical parts 

 which have been adopted ; and this is not of so much 

 consequence, because, although the invention is higlily 

 'i-ius, it has scarcely ever been practically em- 

 1 'Inyod to any extent. Besides the difficulty to which we 

 have alluded, there are others which also interfere with 

 the result; the receiving cloth may be unequally 

 stretched; the two instruments may not commence 

 work together, itc. Messages, however, have been sent 

 accurately through a distance of fifty miles; and as many 

 as 300 letters per minute can be printed by this interest- 

 ing instrument. 



Whilst referring to electro-chemical printing tele- 

 graphs, we may mention a very ingenious arrangement 

 employed by Mr. Whitehouse, whilst he was engaged in 

 trying experiments in connection with the Atlantic 



