NATURAL PHILOSOPHY. 123 



meridian of Washington. The astronomer in New Orleans, and St. 

 Louis, and every other place within the reach of the magnetic wires, 

 may wait for the same star, and, as it comes to their meridian, they h-ivc 

 but to touch the key, and straightway this central magnetic clock tells 

 their longitude. 



" And thus this problem, which has vexed astronomers and naviga- 

 tors, and perplexed the world for ages, is reduced at once, by Ameri- 

 can ingenuity, to a form and method the most simple and accurate. 

 While the process is so much simplified, the results are greatly re- 

 fined. In one night the longitude may now be determined ivith far 

 more accuracy by means of the magnetic telegraph and clock than it can 

 by years of observation according to any other method that has eier been 



In a later letter Lieut. Maury says: " The magnetic telegraph now 

 extends through all the States of the Union, except, perhaps, Arkansas, 

 Texas, and on the frontier ; so that a splendid field is presented for 

 doing the world a service by connecting, for difference of longi'.ude 

 through means of the magnetic telegraph and clock, all the principal 

 points of this country with this Observatory (Washington). In antici- 

 pation of such extension of the wires, I ordered an instrument for the 

 purpose, and it has recently arrived. It is intended to determine latitude 

 also, so that by its means and this clock I hope, during the year, to 

 know pretty accurately the geographical position of Montreal, Boston, 

 Chicago, St. Louis, New Orleans, &e., and their difference of longitude 

 from this place, quite as correctly as the difference between Greenwich 

 and Paris has been established by the usual method and after many 

 years of observation." 



THE COPYING ELECTRO-TELEGRAPH. 



THE specification of the invention, by means of which a letter 

 written in London may be copied lerbalim et literatim in Liverpool, 

 discloses the means by which this is to be accomplished. Wonderful 

 as it seems, to have the power of producing a fac-simile of writing in- 

 stantaneously at any distance, the mode of operation is extremely 

 simple. The writing materials consist of tinfoil, varnish, and a 

 quill pen. The letter thus written is applied to a cylinder; a metal 

 style or point presses on the writing as the cylinder revolves ; and 

 the point being attached to a screw, it moves gradually along from 

 one end of the cylinder to the other. The thread of the screw is 

 sufficiently fine for the point to traverse six or seven times over each 

 line of writing before it passes by the revolution of the cylinder to 

 the next. The point is connected with one pole of a voltaic battery, 

 and the cylinder is connected with the other pole, so that the electric 

 current may pass from the former to the latter : but as varnish is a 

 non-conductor of electricity, the circuit is interrupted whenever the 

 point presses on the varnish-writing. The distant telegraphic instru- 

 ment is an exact counterpart of the one that transmits ; but, in place 

 of the tinfoil, paper, moistened with a solution readily decomposed by 

 electricity, is applied to the cylinder. Thus the electric current trans- 



