C 263 ] 



LIII. Experiments on the Development of Electricity by Pressure; 

 — Larvs of this Deivlopment. By M. BccgUEREL, Ancien 

 Chef de Bataillon du Genie. 



[Continued from p. 211.] 



Comparison of the electric Phccnomena produced hy Pressure 

 •with those presented hy the Exfoliation of certain Mineral 

 Substances. 

 TT is well known that two lamir.fie of mica suddenly separated 

 •* in the dark give out light. No attempt had been made 

 to ascertain any tiling beyond this fact; but if the precaution 

 is taken to make the experiment with each lamina fixed to an 

 insulating handle by means of a little mastic, it will be seen 

 that each, in separating, carries with it an excess of con- 

 trary electricity, and that this excess is greater in propor- 

 tion to the velocity of the sejiaration. These results aie al- 

 waj's obtained, however thin the lamina of mica may be ; it 

 is therefore probable that they would still be obtained in sepa- 

 rating two molecules from each other. The foliated talc of 

 St. Gothard, and the limj^id sulphate of lime of Montmartre, 

 give similar electric results by exfoliation; and it is probable 

 that if we had the means of separating quickly, that is to say, of 

 splitting, all crystallized substances in the manner of mica, each 

 of the parts would retain an excess of contrary electricity; 

 and I doubt not but that the intensity of the electricity deve- 

 loped would bear some relation to the force of the molecular 

 attraction *. 



A severed card presents analogous results. It appears, 

 then, that v.hen certain crystallized substances are exfoliated, 

 electrical results are obtained similar to those afforded by two 

 substances withdrawn from compression: the influence of the 

 velocity of separation is equally felt in these two modes of ac- 

 tion. Is not the development of electricity to be attributed, 

 in both cases, to the destruction of the molecidar attraction? 



If this be the case, the eliect of pressure being to augment 

 that attraction, it would follow that the more strongly these 

 bodies were compressed the greater would be tb.e development 

 of electricity. This is precisely what hajipens, as we shall have 

 occasion to observe in speaking of the laws which regulate the 

 development of electricity by jiressure. 



Two laminit of" mica detached iiom the same piece being 

 put together and jiressed anew, remain after pressure in two 



• Since this memoir has heen drawn up, these phaenomena have rC" 

 ceived nuicli further developnieut ; and the new facts which have been oh- 

 servcd niakf kii^wii the distribuciun of electricity in rcL;iilaily crystaliizcd 

 mineral siilistances. 



different 



