The careful study of other mountain-chains, especially those of the American continent, has shown that the series of actions which we have described as occurring in the Alps, took place in the same order in the formation of all mountain-masses. It is doubtful whether the line of weakness is always betrayed in the first instance by the formation along its course of volcanic fissures. But in all cases we have evidence of the production of a geosynclinal, which is afterwards, by lateral pressure, converted into a geanticlinal, and from this the mountain-chains have been carved by denudation. Professor Dana has shown that the geosynclinal of the Appalachian chain was made up of sediments attaining a thickness of 40,000 feet, or eight miles; while Mr. Clarence King has shown that a part of the geosynclinal of the Rocky Mountains was built up of no less than 60,000 feet, or twelve miles of strata. It has thus been established that a very remarkable relation exists between the forces by which continental masses of land are raised and depressed, and mountain-ranges have been developed along lines of weakness separating such moving continental masses, and those more sudden and striking manifestations of energy which give rise to volcanic phenomena. It is in this relation between the widespread subterranean energies and the local development of the same forces at volcanic vents, that we must in all probability seek for the explanation of those interesting peculiarities of the distribution of volcanoes upon the face of the globe which we have described in a former chapter. The parallelism of volcanic bands to great mountain-chains is thus easily accounted for; and in the same way we may probably explain the position of most volcanoes with regard to coast-lines. We have already pointed out the objections to the commonly-received view that volcanoes depend for their supplies of water on the proximity of the ocean. This proximity of the ocean to volcanic vents we are thus inclined to regard, not as the cause, but as the effect of the subterranean action. The positions of both volcanoes and coast-lines are determined by the limits of those great areas of the earth's crust which are subjected to slow vertical movements, often in opposite directions. Terrible and striking, then, as are the phenomena connected with volcanic action, such sudden and violent manifestations of the subterranean energy must not be regarded as the only, or indeed the chief, effects which they produce. The internal forces continually at work within the earth's crust perform a series of most important functions in connection with the economy of the globe, and were the action of these forces to die out, our planet would soon cease to be fit for the habitation of living beings.