22 Anniversary Address of the 



ceous, but even certain eocene strata, this same heat must 

 have caused many kinds of rock to expand, and might, in this 

 manner, slowly give rise to the sideway thrust exhibited in 

 the curved beds on either flank of the chain. It is now 

 known that granite and sandstone, while solid, expand and 

 contract, even under such a range of atmospheric tempera- 

 ture as the difference of a Canadian winter and summer pro- 

 duce. "We must also take into account that highly inclined 

 or vertical argillaceous strata, such as the flysch, would 

 shrink when heated, and give off their water ; while other 

 rocks, ranged side by side, might be simultaneously expand- 

 ing or partially melting, so as to occupy more room, and that 

 the clays might thus be pressed into solid shales and acquire 

 irregular and complicated curves. The irregularity and con- 

 fusion would be greatly increased by local variations in the 

 composition of the stratified deposits, whether in the direc- 

 tion of their strike or dip, and also by the unequal intensity 

 of the heating and cooling processes, whether the central be 

 compared with the lateral parts of the chain, or the super- 

 ficial with the internal parts. Yet we cannot feel sure, that 

 were such mighty changes now in progress in any range of 

 mountains subject to earthquakes, such as the Andes or 

 Himalaya, we could guess at the direction of the movement, 

 for the contraction or expansion of mineral masses might be 

 carried on as slowly as the growth of a tree or the swelling 

 of its roots in the soil. 



M. de Beaumont, in his essay on volcanic and metallifer- 

 ous emanations,* observes that, according to the experi- 

 ments of Deville, the contraction of granite in passing from 

 a melted or plastic to a solid state must be more than ten 

 per cent. We have here then at our command an abundant 

 source of depression on a grand scale at every geological 

 period in which granitic rocks have originated. All mine- 

 ralogists seem agreed that the passage from a liquid or pasty 

 to a solid and crystalline state cannot, in such cases, have 

 been instantaneous throughout voluminous masses ; yet by 

 suddenly crystallizing alone could it have given rise to the 



* Bulletin d« la Sue. Geol. 2(i Series, vol. vi. p. 1312. 



