April 29, 1875] 



NATURE 



511 



sive to-and-fro motion of the shuttle, superseded the 

 laborious and complicated hand process previously in 

 vogue. An endless band of cards is passed successively 

 over the register of the loom, and brought forward 

 at each throw of the shuttle, each card being perfo- 

 rated with holes to represent that integral portion of the 

 pattern, and each hole controlling the elevation of one or 

 more threads in the warp. A series of weighted needles 

 are, as the holes pass, momentarily allowed to drop, and 

 in so doing by a mechanical adjustment raise the respec- 

 tive threads or groups of threads to the surface of the 

 cloth, so that the shuttle passes underneath, and thus the 

 pattern thrown on the surface is automa- 

 tically repeated as the cards in succession 

 pass over the register. It is this Jacquard 

 loom principle that Wheatstone has em- 

 ployed to weave his electric currents into 

 the line and produce the electric pattern 

 upon his paper at the distant end. The 

 Jacquard loom weaves rapidly, because 

 the mechanical labour incident to the pre- 

 paration of the pattern is carried out before 

 it is placed on the loom. So with the auto- 

 matic printer, or electrical Jacquard, the 

 transmitting speed is rapid. The cards 

 used in the electrical loom to regulate the 

 sequence of the currents and groups of 

 signals are prepared before being passed ? 



through the instrument, so that the time 

 occupied in transmitting any number of , 



currents and groups of currents to repre- ' _ 

 sent letters and words is reduced to a ~ 



minimum. In electrical ti'ansmissions this ^' 



is important, the cost of manual labour - - _ 



per minute or hour being inappreciable as 

 compared to the value of a minute or 

 hour in the occupation of an extended 

 telegraph wire, erected at a cost of 

 thousands of pounds. For instance, a line of poles and a 

 single wire between London and Glasgow would require 

 at least 12,000/. for its erection. To obtain the greatest 

 amount of work out of such a wire in a given time is one 

 of the problems of mechanical telegraphy, and com- 

 mercial success depends greatly upon the speed at which 

 currents of electricity can be sent through a wire of 

 given length. This speed is regulated by the rapidity 

 with which the currents can be transmitted through the 



wire without coalescing, that is, without interfering with 

 each other and running together to form a continuous 

 mark at the distant end. Reference has already been 

 made to the conditions to be observed in the passing of 

 currents into metallic conductors to ensure the maximum 

 of speed, that they should be passed into the wire at 

 equal intervals of time and of equal duration. Now, this 

 is what the electrical Jacquard of Wheatstone so beauti- 

 fully carries out, and the mode by which this electric 

 pattern is woven will now be explained. 



The apparatus consists essentially of three distinct 

 parts — one for the preparation of the electrical loom card 



Fig. 19. — Ti.e " Perforator," for cuttiug out the message on the paper ribbon. 



to regulate the succession and sequence of the currents in 

 the electrical writing ; another, the loom for the passing 

 the currents so grouped into the line ; and the third, the 

 shuttle or pattern- producing arrangement by which the 

 currents so passed into the line are recorded and trans- 

 formed into symbols representing letters, words, and 

 sentences. All automatic high-speed instruments for 

 either submarine or land-wire circuits embody these 

 essential conditions, the mechanical modification of parts 



alone i egulating the character of the apparatus for the 

 work to be performed. The message to be sent is first 

 punched out in holes (arranged to represent the "dot" 

 and '■ dash " of the Morse alphabet) on a continuous paper 

 ribbon by means of an instrument called the " Perforator," 

 shown at Fig. 19, in an elementary form. Each of the 

 three finger-keys on depression perforates a small round 

 hole in the paper ribbon, the right being representative 

 of the dot, the left of the dash, the centre one the 

 mechanical spacing of the holes, and necessary for 



the regular motion of the ribbon through the loom or 

 '' transmitter." 



This perforating machine is so constructed that upon the 

 depression of any one of the keys a threefold action takes 

 place : namely, the paper ribbon in the machine is locked 

 in position to receive the perforation ; secondly, the hole 

 is cut by the pressure on the paper of a steel pin ; thirdly, 

 a mechanical movement, which at first holds the paper 

 in the direction in which the ribbon enters, after the hole 

 is cut automaticaUy, carries it forward the requisite dis- 



