Geologists having unanimously agreed—for perhaps there is not a single dissenting voice—that the chronology of the earth must be greatly extended, attempts have been made to give precision to it. Some of these have been based on astronomical, some on physical principles. Thus calculations founded on the known changes of the eccentricity of the earth's orbit, with a view of determining the lapse of time since the beginning of the last glacial period, have given two hundred and forty thousand years. Though the general postulate of the immensity of geological times may be conceded, such calculations are on too uncertain a theoretical basis to furnish incontestable results.

But, considering the whole subject from the present scientific stand-point, it is very clear that the views presented by theological writers, as derived from the Mosaic record, cannot be admitted. Attempts have been repeatedly made to reconcile the revealed with the discovered facts, but they have proved to be unsatisfactory. The Mosaic time is too short, the order of creation incorrect, the divine interventions too anthropomorphic; and, though the presentment of the subject is in harmony with the ideas that men have entertained, when first their minds were turned to the acquisition of natural knowledge, it is not in accordance with their present conceptions of the insignificance of the earth and the grandeur of the universe.

Among late geological discoveries is one of special interest; it is the detection of human remains and human works in formations which, though geologically recent, are historically very remote.

The fossil remains of men, with rude implements of rough or chipped flint, of polished stone, of bone, of bronze, are found in Europe in caves, in drifts, in peat-beds. They indicate a savage life, spent in hunting and fishing. Recent researches give reason to believe that, under low and base grades, the existence of man can be traced back into the tertiary times. He was contemporary with the southern elephant, the rhinoceros leptorhinus, the great hippopotamus, perhaps even in the miocene contemporary with the mastodon.

At the close of the Tertiary period, from causes not yet determined, the Northern Hemisphere underwent a great depression of temperature. From a torrid it passed to a glacial condition. After a period of prodigious length, the temperature again rose, and the glaciers that had so extensively covered the surface receded. Once more there was a decline in the heat, and the glaciers again advanced, but this time not so far as formerly. This ushered in the Quaternary period, during which very slowly the temperature came to its present degree. The water deposits that were being made required thousands of centuries for their completion. At the beginning of the Quaternary period there were alive the cave-bear, the cave-lion, the amphibious hippopotamus, the rhinoceros with chambered nostrils, the mammoth. In fact, the mammoth swarmed. He delighted in a boreal climate. By degrees the reindeer, the horse, the ox, the bison, multiplied, and disputed with him his food. Partly for this reason, and partly because of the increasing heat, he became extinct. From middle Europe, also, the reindeer retired. His departure marks the end of the Quaternary period.

Since the advent of man on the earth, we have, therefore, to deal with periods of incalculable length. Vast changes in the climate and fauna were produced by the slow operation of causes such as are in action at the present day. Figures cannot enable us to appreciate these enormous lapses of time.

It seems to be satisfactorily established, that a race allied to the Basques may be traced back to the Neolithic age. At that time the British Islands were undergoing a change of level, like that at present occurring in the Scandinavian Peninsula. Scotland was rising, England was sinking. In the Pleistocene age there existed in Central Europe a rude race of hunters and fishers closely allied to the Esquimaux.

In the old glacial drift of Scotland the relics of man are found along with those of the fossil elephant. This carries us back to that time above referred to, when a large portion of Europe was covered with ice, which had edged down from the polar regions to southerly latitudes, and, as glaciers, descended from the summits of the mountain-chains into the plains. Countless species of animals perished in this cataclysm of ice and snow, but man survived.

In his primitive savage condition, living for the most part on fruits, roots, shell-fish, man was in possession of a fact which was certain eventually to insure his civilization. He knew how to make a fire. In peat-beds, under the remains of trees that in those localities have long ago become extinct, his relics are still found, the implements that accompany him indicating a distinct chronological order. Near the surface are those of bronze, lower down those of bone or horn, still lower those of polished stone, and beneath all those of chipped or rough stone. The date of the origin of some of these beds cannot be estimated at less than forty or fifty thousand years.

The caves that have been examined in France and elsewhere have furnished for the Stone age axes, knives, lance and arrow points, scrapers, hammers. The change from what may be termed the chipped to the polished stone period is very gradual. It coincides with the domestication of the dog, an epoch in hunting-life. It embraces thousands of centuries. The appearance of arrow-heads indicates the invention of the bow, and the rise of man from a defensive to an offensive mode of life. The introduction of barbed arrows shows how inventive talent was displaying itself; bone and horn tips, that the huntsman was including smaller animals, and perhaps birds, in his chase; bone whistles, his companionship with other huntsmen or with his dog. The scraping-knives of flint indicate the use of skin for clothing, and rude bodkins and needles its manufacture. Shells perforated for bracelets and necklaces prove how soon a taste for personal adornment was acquired; the implements necessary for the preparation of pigments suggest the painting of the body, and perhaps tattooing; and batons of rank bear witness to the beginning of a social organization.