54 M. Becquerel on the electrical properties of Tourmaline, 



the mode of action of the developement of electricity during 

 the increase of temperature, and that which takes place during 

 the cooling. In both cases the temperature varies every in- 

 stant. 



The most delicate experiments seem to show that the tour- 

 maline, while it is electrified, allows none of the electricity to 

 escape, nor takes any from surrounding bodies. The effects 

 are produced by the separation of the two fluids in each par- 

 ticle. In order to prove that there is no discharge of electri- 

 city from the tourmaline, it is necessary to place upon the up- 

 per plate of an excellent condenser of Volta, a plate-of copper 

 of a high temperature, and place it below one of the extremities 

 of the stone. Some moments after, upon separating the plates, 

 no accumulation of electricity will be found. 



After having studied what passes in a tourmaline of which 

 all the parts are equally heated and cooled at the same time, 

 I now proceed to examine what takes place when one of the 

 sides receives more heat than the other. 



iEpinus and Wilson, as I said before, were much occupied 

 with this question. The contradictory results at which they 

 arrived may be easily explained. To analyse the electrical ef- 

 fects which are exhibited, we must first of all observe if the 

 temperature is increasing or decreasing in the side where it is 

 applied ; for the results vary in each case. This is known by 

 inclosing each end of the tourmaline in a little tube of glass, 

 the ends of which are melted by the blowpipe that they may 

 fit exactly ; it is then fastened by its middle to a tube of glass 

 by a thread of platina. If one of the extremities which is not 

 fitted in one of the little tubes be heated, for instance that which 

 corresponds to the side positive by cooling when the tempe- 

 rature is everywhere the same, and which I represent by P, 

 this side will at first be heated at the expence of the tube, will 

 take the same temperature as it, and will then cool in the same 

 time. In the first case, whilst the temperature does not begin 

 to rise at the other extremity, which I call N, all that part P 

 will be electrified negatively, and the other will be in the state 

 of zero. The tourmaline then possesses but a single electricity. 

 We know this by presenting successively all the points of the 

 tourmaline to the little tinsel discs of the electroscope of Cou- 



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