360 On Crystallography . 



bodies one of which possesses the vitreous and the other 

 the resinous electricity are mutually attracted. 



Amony: the number of bodies capable of receiving elec- 

 tricity by friction, \vc find some, which, after having been 

 simpfv presented to the fire for a moment, or dipped into 

 hot water, have acquired the electrical virtue. These bodies 

 have in this case one side solicited by vitreous electricity, 

 while the side diametrically opposite gives signs of resinous 

 electricity. 



One general observation made on such of the same bodies 

 as are crystallized, consists in this ; namely, that their forms 

 take from the symmtlry of the ordinary crystals, in the 

 same manner as the parts in which the two species of elec- 

 tricity reside, although similarly situated on both sides, 

 differ in their configuration. The one undergoes de- 

 crements which are null on the opposite part, or to which 

 some decrements answer which follow another law. It 

 results that on a simple inspection of one of these crystals, 

 U'e may indicate hcTorehand the side which will give signs 

 of vitreous electricity, and th^t which will manifest resinous 

 .electricity. 



' Electricity separates the whole mineral kingdom into 

 three great divisions, which follow nearly the methodical 

 order generally adopted for the classification of bodies of 

 this kingdom. Almost all the substances known by the 

 names of stones and salts acquire by friction the vitreous 

 electricity, provided they enjoy a certain *(Jegree of purity. 

 The inflammable substances properly so called, with the 

 exception of the diamond, being rubbed in the same man- 

 ner, receive on the contrary the resinous electricity. The 

 metallic substances possess in general in an eipjnent de- 

 gree the conducting property of electricity. A few of 

 then), which being mineralized approach the saline state^ 

 such as carboriatcd lead, also enter into analogy with the 

 salts, by the facuhy of acquiring the vitreous electricity by 

 means of friction. 



I ought to premise that we here allude to the ordinary 

 inethods of exciting electricity ; as when we employ the 

 friction of the hand, or that of a piece of cloth. I sup- 

 pose also that the bodies rubbed are polished; for there 

 are some kinds of quartz, gems, and other analogous sub- 

 stances, such as glass, v\hich acquire the resinous electricity 

 by means of friction when its surface is dull. 



It results from all that has been said, that the electrical 

 property furnishes characters useful in several respects for 

 jtjie distinction of minerals. 



' ' Electricity 





