126 ANNUAL OP SCIENTIFIC DISCOVERY. 



perform ; the same message being of course written either on metallic 

 paper with an insulating ink, or vice versa ; indeed it would be difficult 

 to assign the limits of its application. The fact that the principle 

 upon which the system is based has been tried upon a line exceeding 

 three hundred miles, renders its practicability for long distances no 

 longer doubtful ; and a line between Liverpool and Manchester, 

 England, is, in fact, now constructing for public service. 



Caselli's Copying Telegraph. The peculiarity of this telegraph 

 consists in a pendulum suspended to an endless screw ; a small steel 

 hand being attached to its lower end, at right angles with it. Be- 

 neath it, parallel to it, and at right angles with the steel hand, is 

 placed a metal plate, upon which the dispatch to be transmitted is 

 written in ordinary ink. At the point of destination is a similar pen- 

 dulum, suspended in the same way, and with a similar little steel hand 

 attached in like manner to its lower end. Under this second pendu- 

 lum, parallel to it, and at right angles with its little hand, is placed 

 a sheet of prepared paper, upon which the transmitted dispatch is to 

 be received. When the telegraph is put into operation, the two pendu- 

 lums vibrate simultaneously backwards and forwards across the sur- 

 face of their respective sheets, descending a hair's breadth lower at 

 each vibration. Whenever, in its passage to and fro across the sur- 

 face of the metal plate, jkc steel hand of the first pendulum comes 

 into contact with the ink (which is a non-conductor), the electric cur- 

 rent is transmitted to the second pendulum, and produces, through 

 the steel attached to this second pendulum, a chemical action, which 

 causes a stain upon the prepared paper in contact with it at each 

 point of its surface touched by this second hand during the transmis- 

 sion of the electric current. The form of the letters, or other lines, 

 traced in ink upon the surface of the metal plate at one end of the 

 line, is thus reproduced, in successive rows of minute, dot-like stains, 

 superposed one upon the other so closely as to show like a single 

 stroke (unless examined with a microscope) upon the sheet of paper 

 at the other end of the line. This mode of electric telegraphing has 

 been already attempted in England and France ; but the dispatches 

 received were always so much blurred as to be scarcely legible, and 

 the invention was, therefore, practically worthless. Professor Caselli 

 has succeeded in causing an instantaneous suspension of the transmis- 

 sion of the electric current whenever the first pendulum is passing 

 over those portions of the metal plate which are free from ink; so 

 that the chemical action of the second hand, in its oscillations across 

 the surface of the paper, takes place only at those points which are 

 touched by it during the moments when the electric current is being 

 transmitted. The blackened points of the sheet of paper conse- 

 quently correspond exactly to the points of the metal plate that are 

 covered by the ink ; and thus present a fac-simile of the writing, por- 

 trait, plan, pattern, etc., of the original dispatch, which, by this most 

 admirable development of the electro-telegraphic art, is reproduced 

 with perfect clearness and exact fidelity upon the paper at the 

 further end of the telegraphic line. The cost of establishing such a 

 telegraph is, at present, rather greater than for the Morse and other 

 telegraphs in ordinary use ; but the machinery, when once established, 

 is easily managed. 



