1823.] M. Schweigger's Electromagnetic Multiplier. 443 



this effect, one of the two pieces of metal, a, fig. 8, is combined 

 with two pieces of b, the other, so that this arrangement consti- 

 tutes a broken circuit, the two ends of which are of the same 

 metal. After having put some ice upon one of the solderings, a 

 communication is established between the two pieces b by 

 means of the multiplying wire. 



The effect of this is sensible upon the needle of the instru- 

 ment, but yet it is very weak ; weaker, for example, than the 

 effect of a piece of copper and silver with water as a fluid con- 

 ductor. The effect is rendered more evident by communicating 

 a fresh impulse to the needle, at the end of each return after a 

 former impulse. 



The extraordinary weakness of this action is very remarkable. 

 We learn from this result that the same thermoelectric elements 

 which produce a great effect upon the magnetic needle of the 

 compass, when their communication is made by a short and 

 thick conductor, act but very little even upon a much more sen- 

 sible needle, when the communication is made by a thin con- 

 ductor of considerable length. A hydroelectric current excited 

 by a piece of zinc and silver, with water as a fluid conductor, 

 produces an effect upon the needle perhaps a hundred times 

 greater than that of the thermoelectric current; nevertheless the 

 effect produced by the former upon the needle of the compass, 

 even when the communication is made between the elements by 

 the best conductors is scarcely sensible ; while the effect of the 

 latter upon the compass is not only sensible but considerable. 

 All this marks a very important property of the thermoelectric 

 current, which indeed might have been foreseen by theory, but 

 which experience should confirm ; that is to say, the thermo- 

 electric circuit contains the electric powers in much greater 

 quantity than the hydroelectric circuit of equal size ; but, on the 

 other hand, the intensity of force in the former is much weaker 

 than in the latter. Since the first electromagnetic experiments, 

 it has been clearly seen that the deviation of the needle pro- 

 duced by the electrical current would be regulated accord- 

 ing to the quantity of electric power, and not by its inten- 

 sity. Thus the considerable deviation which the thermo- 

 electric current produces is an indication of the great quan- 

 tity of power which it contains. As to the intensity, it is 

 universally acknowledged, that an electric current pervades con- 

 ductors so much the more readily as it is more intense : the hydro- 

 electric current which more easdy pervades the wire of the multi- 

 plier than the thermoelectric current does, must, therefore, be 

 more intense. The much greater quantity of electric power which 

 must be admitted to exist in the thermoelectric current, will form 

 no objection to this reasoning ; for it is perfectly evident that in 

 the case in which a current A, of intensity equal to that of an- 

 other current B, but greater in quantity, is presented to a con- 

 ductor sufficient to transmit the quantity of B. only ; this 



