AMERICAN ELECTRIC-TELEGRAPH. 273 



ihe facts and laws of Electro-Magnetism previously known, it may, per- 

 liaps, bcmost interesting to our readers to explain these in the historical 

 order of their developement or discovery. 



In 1790, Galvani made the discovery of the developement of elec- 

 tricity by the contact of two different metals and a moist substance with 

 each other; and, soon after, Volta, taking this discovery and following 

 up the train of his own reasoning, constructed his jnle^ by which a con- 

 tinued current of electricity was brought under the power of the oper- 

 ator. T\\c pile of Volia, as mochlicd and improved by others, has been 

 called indifferently the Galvanic and Voltaic hailcry. This diflers, as a 

 source of electricity, from the ordinary electrical machine principally 

 in this respect, that it aflbrds to the operator a continued slreavi of elec- 

 tricity capable of being put in motion or stopped at will, which cannot 

 be effected with the latter, except with the utmost dilficulty anil for a 

 very short time. As this is the generator of the power applied, it will 

 be described in the form used in the working of the telegraph. From 

 three to five glass tumblers, about three inches high .and two inches and 

 three quarters in diameter, constitute the containing vessels. Into each 

 of these is placed a piece of the purest zinc, bent or cast so as just to 

 go into it and of the same height; within this is placed a cup, an inch 

 and a quarter in diameter, of earthen ware, baked without I)eing glazed, 

 so that moisture can soak but not leak tluoiigh it; and in the inside of 

 this is placed a plate of platinum of the height of the cup and about as 

 thick as tinfoU. These cups, which may be num')crcd 1, 2, .3, 4, &c., 

 are arranged close to each other ; and the zinc of No. 1, connected with 

 the platinum of No. 2, l)y a metallic strap soldered to each ; the zinc of 

 No. 2, is similarly connected with the platinum of No. 3. &c.; and the 

 zinc of the last is made to communicate with the platinum of No. 1, by 

 means of a wire. This wire may be of any length desirable, from one 

 inch to thousands of miles, provided it is well joined to the extreme 

 metals. Instead of using but one fluid to act upon the two metals, as in 

 the experiments of Volta, it has been found that the best and most endu- 

 ring effect is produced, when the porous earthen cup containing the pla- 

 tinum is filled to within one quarter of an inch of the top with pure ni- 

 tric acid, and the part of die tumbler, in which the zinc is, to the same 

 height with sulphuric acid diluted with twelve parts of water. The 

 electricity passes from the zinc in each tumbler to the platinum in the 

 same, thence through the strap of metal to the zinc of the next, &c., 

 and at last from the last platinum through the wire round again to the 

 first zinc, constituting a circuit through which it is irremittcdly flowing 

 when the buttery is in action. The electricity, whilst flowing through 

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