Page:Popular Science Monthly Volume 20.djvu/137

Rh , 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 afterward, 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 forty thousand 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 sixty thousand 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. . ..

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. . ..

It is by no means a difficult task to calculate the approximate rate at which the various continents and islands are being leveled down, and such calculations prove that in a very few millions of years the existing forces operating upon the earth's surface would reduce the whole of the land-masses to the level of the ocean. . ..

But, by the admirable balancing of the external and internal forces on our own globe, the conditions necessary to animal and vegetable existence are almost constantly maintained, and those interruptions of such conditions, produced by hurricanes and floods, by volcanic outbursts and earthquakes, may safely be regarded as the insignificant accidents of what is, on the whole, a very perfectly working piece of machinery.



years ago there appeared a portly volume, profusely illustrated, and entitled "The Ancient Stone Implements and Ornaments of Great Britain." It was a monument of careful observation and painstaking labor in a new field, with not many enthusiastic explorers, and was at once accepted as a trustworthy and authoritative work upon the subject, which, although chiefly confined to Great Britain, was an important contribution to the general science of archæology. Mr. John Evans, the author of that work, has continued to devote himself to the field of archaic research, and now publishes a corresponding volume on "The Ancient Bronze Implements, Weapons, and Ornaments of Great Britain and Ireland."

We have here a history more ancient than written history, and which reveals the social state, the conditions of culture and development of prehistoric man. These are determined by the evidences of what he did, the relics that remained-and have been found, of what he invented and constructed to meet his wants. His first tools and weapons were of stone, and the period when he employed them is the earliest of which we have any trace, and is called the "Stone Age." But there was an education in these rude constructions which led to progress, so that this most ancient period has been divided into two stages, the Palæolithic or the very earliest, and the Neolithic or later stone age, which exhibits a marked advancement in the art of producing stone implements. 