“The discussion of this question opens up for our consideration the examination of the geological structure of these oscillating terranes, as to what these are made up of, and it is evident that we must reach some general conclusion as to the succession of the strata composing them, and their relative positions to each other, as whether they are, in the language of stratigraphy, conformable or unconformable. The inference and argument are simple. If we find that the rocks composing these sections are crystalline, ancient, and deeply bedded formations, presumably coexistent, so to speak, with the original or very early formative beds of the world, and referable to its beginnings, we are permitted, by all the analogies of induction and deduction, to assume that these rocks have at least a relative stability. On the other hand if our examination reveals the fact that they are recent deposits, more or less unconsolidated, easily disturbed in their positions, easily readjusted in their molecular or physical structure, then by the most unexceptional and matter-of-fact observation, we shall regard them as questionably permanent, indeed as unmistakably non-resistant to the subterranean forces of terrestrial mutation. “Again it is clear that a pile of bricks, or of any other superimposed building blocks is the more secure, in its equilibrium, if the component parts overlie each other, along the broadest surfaces, and come in contact, or _fit_, as we say, in parallel position. If these bricks succeed each other in lines of brick that are flat, and then in lines that are vertical, or placed on their thinnest and narrowest edges, and these two contrasted positions alternate, or are irregularly disposed with reference to each other in the same wall, such a construction implies, involves, elements of weakness, and under the shock of any incident force would succumb in ruin more quickly, and more irretrievably than the former. If further, the latter building style had suffered ruptures and dislocations and the gaps or openings and broken surfaces of contact between its parts had been invaded or replaced by an irregular or incongruous assortment of ‘filling,’ differing from the original bricks in substance, texture and hardness, then we have a third pattern of composition that again is weaker than either of its predecessors. But further. If this least massive and most vulnerable type of structure has been subjected to repeated and considerable strains of elevation and depression, and strains recurrent at short intervals, then, without inspection, we know that its interior coherence has been much shattered, and that it has undergone a progressive dilapidation.