IS2 Dr Bouevs Geological Comparative View of' the 
as aggregate fragments of more ancient rocks, or of the first 
oxidated crust of the earth, might it not be possible that ig- 
neous agents had, before, after, and simultaneously, with the 
granitic eruptions, acted upon the slates, and produced in them 
a kind of change ? Heat and gaseous emanations would have 
given, especially under strong compression, a kind of igneous 
liquefaction to slate, similar to that observed by De Dree in 
his experiments. The elements of the slates having lost a part 
of their cohesion, caloric and subterraneous emanations would 
have occupied the void spaces ; chemical affinity would have 
exerted itself within limits fixed by the force of cohesion, 
and the constituent parts of rocks would have been able to 
assume, in the liquefaction or slow cooling, an arrangement more 
or less crystalline, according to the accessary circumstances, 
without losing much of their primitive slaty structure. This 
action of chemical affinities, assisted by foreign matter, intro- 
duced by a kind of sublimation, would have given rise to a 
number of species and subspecies of crystalline minerals, dis- 
seminated in nests or in small veins, and only a very small 
number of other minerals would have been posteriorly formed 
in it, by aqueous infiltration. According to this theory, the 
subterraneous agents would have been always decreasing in 
energy from the granites to the basalts, which would depend 
upon the change that had taken place, during the lapse of time, 
in the crust of the earth, owing to the want of compression, 
and the greater mass of solids accumulated upon it 
This hypothesis explains the facts in a manner agreeable with 
geological, chemical, and physical knowledge. The inequality 
of these effects would have given rise to arenaceous, or even ve- 
getable deposits, mixed with crystalline (Tarentaise), and ex- 
plains the passage of crystalline into transition slate. The iden- 
tity of the materials of these rocks with those of granite ; the che- 
mical composition of various subspecies of minerals, minerals 
being more crystallized in the truly crystalline rocks than in 
those which are less so ; the mutual insertion of various crystals 
of two different substances ; the made, the scoriaceous surface 
of minerals (augite, Pyrenees and Scandinavia) ; the scapo- 
lites surrounded with a slaggy crust of augite ; the identity of 
the disseminated minerals in gneiss and granite ; the connection 
