M. Becquerel on the electrical propertiea of Tourmaline, B5 



lomb, charged alternately with positive electricity and negative 

 electricity. 



Its state of electricity is then sensibly the same as that of a 

 Voltaic pile of which the positive pole is in communication 

 with the earth ; because the negative electricity goes on dimi- 

 nishing to the opposite pole. This effect is only produced when 

 the temperature goes on decreasing, and the side opposite to 

 that which has been heated has not attained sufficient tempe- 

 rature to develope also electricity. In the pile only one sort of 

 electricity is obtained every time that one of the poles com- 

 municates with the common reservoir ; it is not so, however, 

 with the tourmaline, which neither gives out electricity nor 

 takes it from surrounding bodies. This fact is in contradiction 

 to our present knowledge of the developement of electricity, 

 which is never found except in two fluids. It follows, then, 

 that in this case there must be one masked or absorbed by 

 the air. but I have never found this indicated by the most 

 delicate observations. It is certain, however, that a single kind 

 of electricity can be produced from one of the sides of a tour- 

 maline without the other acquiring any ; and consequently, 

 without our considering the state of this last as transitory, that 

 is to say, passing from one electrical state to another. 



I have supposed that the side N had not yet acquired a 

 sufficient temperature to produce any electrical effects ; but if 

 it continued to increase, the side would acquire the positive 

 electricity which it should have had if the temperature had 

 been equally increasing in the whole tourmaline- 



I return now to the side P, whose temperature I have sup- 

 posed to be increasing. As soon as it is become stationary its 

 electricity ceases, and afterwards begins again in an opposite 

 direction, when it decreases. At the same time, the side N, ac- 

 cording to the temperature, will be at zero, or possessing elec- 

 tricity positive or negative. I conclude from all these facts, 

 that when the two sides of a tourmaline are heated unequally, 

 each of the two acquires an electrical state independent of the 

 other, and is such, that, if the side P for instance has a tem- 

 p^ature at first increasing, then stationary and decreasing, it 

 will become negative, zero, and positive. The side N, under 

 the same circumstances, that is, if its temperature be increasing, 

 stationary or decreasing, will have a contrary electricity. The 



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