heated matter but cannot convert matter which is in a fluid or viscous state from heat, into a solid, It would retain the moving property of a fluid so long as it retained its heat.
If the behaviour of the internal mass of the earth during the process of cooling was similar to that of lava or basalt,
- (1.)—The solidification would commence at the surface.
- (2.)—The matter in passing from the liquid or viscous to the solid state would attach itself to the parts already solid, i.e., to the under surface of the already solid crust.
- (3.)—The matter in becoming solid from loss of beat would for the most part contract.
- (4.)—The process of cooling and solidification would not take place regularly, owing to the difference in temperature at which different substances become solid, and the difference in the conductivity of different parts of the crust overlying the heated matter.
- (5.)—The solidified portion of the crust would press on the liquid or viscid interior until it became self-supporting.
- (6.)—Gravity would require the several parts of the crust to be in equilibrium. The disturbance of the equilibrium of the crust by irregularity in its growth would be restored by the action of gravity upon it.
The elevation of continents and mountain chains, and the formation of deep oceanic areas and other synclinal depressions, are produced by the long continued action, in a particular direction, of lateral or horizontal pressure or compression resulting from the sinking of the cross on the contracting internal mass on which it rests. The effect of lateral pressure is shown both by the minute plication of laminated strata, as in the cuttings through Lias clay of the new railway between Cheltenham and Banbury, of in the folding of a large expanse of surface as shown by Professor Danya to have been the way in which the Alleghany Mountains wore formed. The parallelism of mountain ranges, and of the outcrop or strike of strata in the same area, which results from the action of lateral pressure upon the crust in the same direction, is well illustrated in England.
The change in the movement by which any area which has been previously elevated undergoes depression, or vice versa, implies a change in the conditions by which the action of lateral pressure is directed. Such changes are caused by irregularity in the growth of the crust and the consequent disturbance of its equilibrium. Such changes could not be produced by the mere settlement of dead materials into a more compact state. Such a process of consolidation would commence at the centre and progress up~wards, and when the interior had once become compact, no undulation of the surface would be possible. With such a condition of the inferior the surface of the earth could not be changed. It would he levelled by denudation, and the ocean would spread over the whole. Terrestrial life would cease to exist for want of a footing. A self-supporting crush would be equivalent to a solid earth, The undulatory movement of the crust was greater in early geological periods than now, the Cambrian and Silurian strata comprise deposits of some six miles
