5*0 Analyjis of the MdliU or Honigjidn: 



other hand, I put into the folution of the fame fait the acidulous oxalate of pot-afli ; but 

 no precipitation was feen. Now thefe different effefts muft afford doubts fufficiently ftrong 

 refpefting the identity of the acid of honigftein with that of forrel : and I muft confefs, 

 that I fhall fufpend my judgment in this matter, notwithftanding the difpofition I had at 

 firfl to believe, that thefe two acids are of the fame nature. Before we decide, we muft 

 therefore wait for new proofs derived from a larger fcale of experiments, in order to throw 

 a more decifive light on the fubjeft. 



Cit. Hauy has carefully examined this fubftance. Some cryftals of it were prefented to 

 him by M. Abildgaard, and he procured fome others from the colle£lion made in Germany 

 by Cit. Launoy. He has difcovered, that the mellite has a very obvious double refradtion, 

 whence there arifes a diftinft chara£ter between this mineral and amber, of which the re- 

 fraftion is fimple. He has obferved likewife, that the cryftals of mellite being infulated, 

 acquire with much facility the refmous eledlricity, but he was not able when they were 

 not infulated, to excite in fome of them more than a weak and varying eleflricity ; fo 

 that it was neceflary to bring quickly together the cryftal and fmall copper needle that is 

 tifed iu thefe kind of experiments, in order that the latter may be more fenfibly attrafted. 

 What feveral learned men have advanced, that this mellite is not rendered eleftrical by fric- 

 tion, is not exaftly true : it may then acquire an eleftricity of the fame nature, as that of 

 amber, but it would be confiderably weaker if the cryftal be not infulated. 



According to the obfervation of the fame naturalift, the primitive form of the mellite 

 determined according to the pofition of the natural junftures, is that of a redlangular odta- 

 hedron, in which the incidence of the face of one pyramid with the face of the other, is 

 about 93f °. This oCtahcdron is fometimes truncated by means of a decreafe, by an ar- 

 rangement on all its foHd angles, in which cafe the two facets which are placed on its 

 fummita are often curve lined. When that the diminution only adls on the four lateral 

 angles a dodecahedron is produced, which confiderably refembles the rhomboidal figure. 

 Suppofing this refemblance perfeft, this would be a fourth origin of that dodecahedron, 

 which exifts as primitive in granite and fulphurated zinc, and has in other fubftances, 

 where it becomes a fecondary form, fometimes as nucleus a cube, and at others a regular 

 odahedron. 



Bulletin des Sciences ^ No. 43. An. 9. 



SCIENTIFIC 



