The commonly accepted theory of the origin of granite is that, in view of indications that it had been subjected to great pressure, it was formed deep in the earth's crust in a molten state, and, after consolidating, thrust up through it, or exposed at the surface by denudation. This theory is not altogether satisfactory, being equivalent to an assertion that a stately building was first constructed and its foundation laid afterwards. Like some other unsatisfactory theories, it has been so often reiterated that it is tacitly assented to as authoritative, on the principle, we suppose, that what everybody says must be true. There are existing conditions analogous to those under which the trappean rocks were formed, as illustrated by modern submarine and subaërial erupted rocks; but the conditions under which primitive granite originated are not now represented in any part of the world.