19. The first effect of the cooling process was to solidify the outermost surface of the melted mass, and to form there a resisting crust, which, thin at first, little by little thickened. This crust constitutes the stone called “granite,” of an extreme hardness, named thus by reason of its granulated appearance. The three principal substances found there are feldspar, quartz or crystal rock, and mica. This last has a brilliant metallic tint, although it is not a metal.
The granite-bed is then the first ever formed upon the globe, which it entirely envelops, and of which it constitutes in some sort the bony framework. It is the direct product of melted matter consolidated. Upon it and in the cavities that its violently agitated surface presented are successively deposited the beds of other rocks subsequently formed. That which distinguishes this from later formations is the absence of all stratification; that is to say, it is in its whole extent a compact and uniform mass, and not divided by different kinds of beds. The effervescence of incandescent substances must have produced numerous and profound crevasses through which this substance was expelled.