124 ANNUAL OF SCIENTIFIC DISCOVERY. 



initted through the ordinary telegraphic wires is made to pass from 

 the metal points to the cylinders of the two instruments, through the 

 interposed moistened paper on one, and through the tinfoil on the 

 other. When the metal point of the transmitting instrument is press- 

 ing on the bare tinfoil, the electric circuit is completed through the 

 paper on the distant cylinder, and by the decomposition of the solu- 

 tion a mark is made; when the point is pressing on the varnish, the 

 circuit is interrupted and the marking ceases. In this manner, the 

 point of the transmitting instrument, by passing several times over 

 each line in different parts from the top to the bottom, produces an 

 exact copy of the forms of the letters; the writing appearing pale- 

 colored on a dark blue ground, consisting of numerous lines made 

 spirally round the cylinder. 



It is essential to the correct working of the instruments that they 

 should rotate exactly together, and this Mr. Bakewell has accomplish- 

 ed by the regulating power of electro-magnets brought into action at 

 regular intervals by means of pendulums. By means of a guide-line 

 the operator at the copying-station can tell with accuracy whether his 

 instrument is moving foster or slower than the other, and thus regu- 

 late the pendulum. Cylinders six inches in diameter may be regula- 

 ted to revolve thirty times in a minute and produce distinct copies of 

 writing. The rate of copying gives 400 letters per minute with a 

 single wire, and with two wires and two points that number would be 

 doubled. London Spectator, June 23. 



NEW TELEGRAPH. 



A MR. JOHNSON, of Oswego, has invented a new machine for tele- 

 graphic purposes. The principle of it is new, in the fact that it uses 

 shot, or the dropping of shot, to make marks, indentations, or signs, 

 on a white sheet of paper. The motive-power of electricity, or of 

 magnetism, Mr. Morse does not presume to patent, but he has patent- 

 ed the use of it for making signs, and what we call the power of in- 

 vigorating the current of electricity by relays of batteries. Mr. John- 

 son uses the common motive-power of electricity to drop his shot, but 

 when the shot are dropped, then another very simple arrangement 

 makes with them the mark on the paper. These shot return in an ever- 

 revolving wheel, and thirty of them do all the work. 



THE COAST SURVEY AND THE MAGNETIC TELEGRAPH. 



ON the fourth day of the sitting of the American Association at 

 Cambridge, Mr. S. C. Walker, Assistant of the U. S. Coast Survey, 

 at the direction of the Superintendent, communicated the substance of 

 his recent Report on the Experience of the Coast Survey in regard to 

 Telegraphic Operations. We give all that seems important. 



" The first mention of the electro-magnetic telegraph, in connec- 

 tion with longitude operations, as far as I know, was made, in 1837, 

 by M. Arago to Dr. Morse. The first practical application of the 

 method was by Capt. Wilkes, in 1844, between Washington and Bal- 



