Crystalline Silicide Bocks. 167 



phyry, amygdaloid, &c., &c., have become what they now are 

 from a melted condition, because this opinion alone is satis 

 factory to the chemists. 



Thus is this important matter settled ! 



But if the case is, that we need not at all assume any thing 

 as to the mode of formation of these rocks ; that, on the con- 

 trary, by the study of their geognostical relations in a reason- 

 able manner, perfect certainty can be obtained in regard to this 

 problem, at least up to a point, which in the mean time 

 must be sufficiently satisfactory to geologists ; and if it is the 

 case, that chemistry, on its part, is precisely not in a position to 

 deliver a safe videtur in this matter — then does this mode of 

 proceeding not betray either a want of knowledge, a deficiency 

 of sound judgment, or a wilful opposition to what is right % 



And should it, moreover, be the case, that the really un- 

 prejudiced chemist will not be pre-eminently, much less ex- 

 clusively, satisfied by the hypothesis spoken of, that at least 

 he cannot consider it as chemically more suitable than the 

 result which can be obtained by geological investigations on the 

 subject, then must the accusation made receive still more 

 weight. 



He who studies the geognostical relations of the unstrati- 

 fied crystalline silicide rocks, will undoubtedly meet with 

 many obscure appearances, and with many circumstances 

 which seem suited only to envelope the subject in dark- 

 ness ; let him, however, but pursue his investigations with 

 assiduity, with reflection, and with the sole view to discover 

 the truth, and he will find it to be a certain matter o/'/ac^that, 

 with a few, partly undoubted, partly problematical, exceptions, 

 these rocks also became what they now are, by having been, 

 so to speak, twice formed, first of all, by any of the usual modes 

 by which rocks are almost formed before our eyes ; and next, 

 by an alteration which proceeded on the very spot, in conse- 

 quence of causes which are still unknown, whereby these rocks 

 received their present petrographical character, which just 

 constitutes the difficult part of the subject. It may be dis- 

 agreeable and disheartening to us, to be obliged to receive 

 into our science an incomprehensible position founded on ex- 

 perience, and which must stand there as such in all its naked- 



