35*5 Hints for the Formation of 



follow, that the metal arrives at the veui by filtering itfelf" 

 through thefe fides } 



24. Is it true that, in mountains of granite, the grain of 

 the granite is finer and the ftone more tender in the neigh- 

 bourhood of a vein ? 



35. Are there obferved in any mine proofs that fubterra- 

 nean fires have contributed to its formation by fubliming the 

 metallic fubftances, or by melting them? In a word, are 

 there feen there any traces of the action of lire ? 



26. In the greater part of mines do we not, on the con- 

 trary, obfcrve proofs of the aftion of water in the fituation ot 

 ■minerals and cf tlicir matrices j in ihcir Jn/fs (groups of cry f- 

 tals), and in the ftate, form and nature of their cr)'ltaHiratlon ? 



27. Does there prevail, at the bottom of mines, a heat fu- 

 perior to the mean temperature of the earth ? Andiffueh 

 a heat exifts in any mine, may it not be explained by 

 that produced bv the lamps; by the miners themfelves ; 

 by fome accumulations of pyrites, or fome local refervoir? 

 of water, without having recourfe to a general caufe or cen- 

 tral fire ? 



28. Is it certain that, in general, veins decreafe in thick - 

 nefs in proportion as they proceed to a greater depth, and 

 terminate in fuch a manner that the fiflures which contain 

 them are doled at the bottom? Were this fact ellablifliedj 

 would it deilroy the poffibility of fubliniations arifing from 

 the intcvior parts of the earth * ? 



zg. In mines which proceed by ftrata, to obfcrve their 

 nature, €X;.ent, thicknefs, inclination, and depth; thefr-in- 

 terruption by the veins, that interfeft them ; their alternate 

 fwellines and conftriclions, as well as the augmentation and 

 diminution of their richnefs, and the figns which precede 

 thefe changes. 



« j8. A. Do there exift veins of from ten to twentv fathoms and 

 more in thicknefs .' or have not metalliferous banks or fiflures between 

 two diffcrtnt kinds of ftone been uk n for veins ? C. 



30. Whe- 



I 



