116 M. Fournet's Opinions on the 



the micaceous eurites, rocks which are almost entirely com- 

 posed of felspar, and finally, the minette, a very fusible augitic 

 and hornblendic rock, and which might traverse all the prece- 

 ding rocks without being in a solid state. 



Here, then, as the result of those laborious and learned re- 

 searches, we see very remarkable phenomena and consequences 

 exhibited in the district round Arbresle. We find the epochs of 

 elevation accurately determined ; also relations established be- 

 tween the eras of these elevations, their direction, the nature of 

 the upraised strata, of the rocks which uplifted them, the veins 

 which are met with, and even respecting the chemical nature, 

 the degree of fusibility, and the epoch of the appearance of the 

 rocks of eruption. 



These investigations form the first portion of the memoir of 

 M. Fournet, and, according to our views, they constitute the 

 most important part of it. But this able chemist as well as 

 geologist, has endeavoured to push much farther the study of 

 the effects which the upraising rocks, at the moment in a state 

 of high temperature, produced upon the strata which they tra- 

 versed ; and from this examination he has drawn new conclu- 

 sions, which, if they cannot be regarded as so well established 

 as the former, are supported at least by very curious facts, and 

 manifest the great acuteness of the observer. 



M. Fournet imagines that argillaceous slate is the true and 

 the only original sedimentary rock, and that this rock, which 

 contains the elements of mica, and frequently plates of that 

 mineral itself, being altered or modified in different ways, 

 either by new combinations or by the expulsion or diminution 

 of one of its elements, or finally by the introduction or the com- 

 bination in the previous mass of certain new elements, it may 

 be so transformed into gneiss, mica-slate, clay-slate (pliyllade), 

 &c. If M. Fournet had been content with announcing these 

 views as possibilities which were deduced from chemical action, 

 we should have listened favourably to the hypotheses offered by 

 a man so celebrated as a metallurgic chemist, and probably would 

 have taken no notice of them in this report. Since, however, 

 the author has endeavoured to support them by adducing facts, 

 we must attempt to determine the value of these facts. 



M. Fournet first dwells upon the varieties which this same 



