From what we know about the cooling of the earth and its geological structure, it would seem very probable that the principal features which we now see upon the surface of our planet, as, for instance, the continents and ocean-beds, received their forms in very early times, being, in fact, more or less a primary result of contraction. Since the formation of these impressions, contractions have continued to take place, and secondary results have come about, the character of which would appear in a great measure to be dependent upon the primary results by which they were preceded. Amongst the secondary results I would point to the position occupied by many volcanos.