334 THERMO-ELECTRICITY. SECT. XXXIII. 



to one end of this apparatus, the other remaining at its natural 

 temperature, currents of electricity flow through each pair of 

 bars, which are conveyed by wires to a delicate galvanometer, the 

 needle of which points out the intensity of the electricity con- 

 veyed, and consequently that of the heat employed. This in- 

 strument is so delicate that the comparative warmth of different 

 insects has been ascertained by means of it. 



The conservation of force is strictly maintained throughout the 

 whole science and different forms of electricity. In static elec- 

 tricity the positive and negative forces exactly balance one 

 another ; they are always simultaneous, and related often by 

 curved lines of force ; there is no defect or surplus, and the ex- 

 istence of one kind without the other is utterly impossible it is 

 absolutely a dual force. The very same may be said of electric 

 currents, whether produced by the Voltaic battery or in any other 

 way the current in one part of the circuit is absolutely the same 

 in amount and dual character as the other ; and in the insulated 

 Voltaic battery, where the sustaining power is internal, not the 

 slightest development of the forces of either of these can occur 

 till the circuit is completed or induction allowed at the extremi- 

 ties ; for if when there is no circuit the induction be prevented, 

 not merely no current, but no quantity of electricity at the poles 

 ready to produce a current, can be evolved in the slightest 

 degree.* 



* Faraday. 



