114 M. Fournet's Opinions regarding the 



which M. Fournet, along with M. Voltz, has denominated Mi- 

 nette. 



The author next inquires into the causes, or rather what are 

 the kinds of rocks which, ejected from the bowels of the 

 earth, have upraised, by their eruption, the stratified rocks, 

 that principally compose the first axis, and which have broken 

 up and overturned the mechanical rocks (roches clastiques) 

 that form the chief mass of the second type. He has also re- 

 cognised, in the district he describes, a great number of gra- 

 nitic and porphyritic masses, and of traps, which, by their mas- 

 sive structure on the great scale, by their penetration, some- 

 times in great dikes, and sometimes in simple veins across the 

 mass of elevated chains, and even in the midst of the coal for- 

 mation (as at Sainte Foy TArgentiere), indicate both the cause 

 and the epochs of these elevations. 



The rocks which the author describes as constituting the 

 principal part of these formations of eruption or of elevation, 

 are common granites, porphyritic granites, which have evidently 

 preceded the quartzose porphyries, and the rock which M. 

 Voltz has elsewhere described under the name of Minette, — a 

 rock which may perhaps be referred, without any new designa- 

 tion, to that which one of us, the reporters, has long ago deno- 

 minated spilite.* At the same time the minette does present, 

 in its varieties and modifications, some peculiarities which do 

 not belong to the rocks known under the names of whinstone, 

 blatterstein, varioUte, corneenne (aphanite), and spilite. These 

 differences are owing to the presence of bronze mica, and, in 

 some cases, to the abundance of acicular hornblende. This rock, 

 of which M. Fournet supplies a minute account, appears to 

 have been the last which appeared, and to have produced the 

 elevations from north to south, or that which constitutes the 

 third axis. Finally, in decomposing first in a spheroidal 

 shape, and then into clay, the minette exhibits new and addi- 

 tional relations with the basalts and the spilites. 



Metallic separations, sublimations, and productions, so de- 



* The spilite of Brongniart consists of a basis of aphanite, containing imbedded 

 portions and veins of calcareous spar, besides various other accidental mine- 

 rals — in short, a variety of amygdaloid. — Edit. 



