120 On the Electricity of Metallic Substances. 



The exterior metatarsian articulates only with the cuboid, 

 and touches by two facets of the exterior edge of its head 

 the middle metatarsian ; the latter is articulated only with 

 the e;reat cuneiform, and by the exterior to the supernume- 

 rary bone, for which it has only one facet. 



The phalangia are broader than long*. 



XIX. Observations on the FAcctricity of Metallic Sab- 

 stanies. By M. IlAUi'f. 



JL HE different methods of exciting in bodies the electric 

 virtue, furnish characters from which great advantage might 

 be derived in regard to the distinction of minerals ; the most 

 remarkable is that which results from the electricity pro- 

 duced by heat, and which hitherto has been observed only 

 in six species of minerals, viz. tourmalin, borated magne- 

 sia, topaze, mesotype, phrenite, and oxidated zinc. An- 

 other method of exciting the electric virtue consists in fric- 

 tion, to which idio-electric substances are subjected. This 

 virtue, as is well known, is of two kinds; one which we 

 call vitreous electricity, and which belongs in general to 

 earthy and acidiferous substances, and another distmguished 

 by the name of resinous electricity, and which characterizes 

 more particularly non-metallic combustible substances, the 

 diamond excepted, the electricity of which is vitreous. 

 Other substances are non-electric, and, to acquire the elec- 

 tric virtue, have need of being brought into communication 

 with a conductor already cnrlowed w'ith that virtue. Metals 

 in the metallic state possess, in an -eminent degree, the 

 faculty of becoming electric in this manner, which may be 

 employed to detect a metal concealed in a stony substance. 

 This is the case with iron, which enters into the composi- 

 tion of jasper, and the presence of which is announced by 

 the sparks emitted by the stone on the finger being applied 

 to it, while it is in contact with an electrified conductor. 



I conceived the idea of employing in another manner the 

 electricity of metallic substances, by insulating them, and 

 rubbing them over an idio-electric substance. The latter 

 then acquires an electricity, the kind of which varies ac- 

 cording to the nature of the metal used as a rubber; and by 



• Length of the calcaneum at its exttiiur edge - o'lj 



lirea-ith of Its articular Kce - -009 



Breadrh of the astragalus - - o-o8 



Lengthof the middle bune of the mituatsus - 1 'lij 



Lcngih of the middle finacr - - on 



+ Fro.ii Annaks du Nlineiim Nuiioiial d Hi 5: aire Nalurcl-'f, No. 17. 



3. necessary 



