Page:Popular Science Monthly Volume 10.djvu/605

Rh race as identity of culture, while there is-great probability that both are implied. We must remember that as we go back in time we should find the races of men less numerous than at present—the nearer we get to the common stock from which it is believed all mankind must have sprung. The survival of stone implements is not unlike the persistence of older forms of life. The gar-pike (Lepidosteus bison) still inhabits our lakes, but the age when the ganoid type of fishes prevailed has long gone by. In order to make the age of the North American rough-stone implements clear, we must study the geological evidence.

Clay and gravel are made, we know, from the primitive rocks. The atmosphere and the rain loosen large pieces of rock from the mountains, and they are broken in the beds of streams by the action of the water. The fine particles are produced by the rubbing of the stones together; the water grinds the broken rocks down smooth, and makes pebbles of them. Gravel, sand, and clay, produced in this manner, become sorted out by the action of the water, or stratified. From a study of the action of existing glaciers or ice-masses on the Alps, or in the North, it is seen that clay and gravel are also made from the primitive rock, ground out by the slow movement of the ice. The mass of dirt and stones is discharged at the edge of the glacier much as a bar is formed by a river.

But there is this difference, that the bar made by the glacier, and which we call a moraine, contains its gravel and clay and bowlders, in a confused mass, with little sorting, and thus unstratified. Now, these rough-stone implements have been found in New Jersey by Dr. Abbott, in unstratified beds of material, which are evidently, from their composition, ancient moraines. There are, we know, different degrees of evidence. A fact may be either demonstrated, or shown to be probable, or possible. I leave it to you to judge whether these circumstances do not demonstrate that North American rough-stone implements are as old as the beds in which they are found. To me, it seems clear that the men who used these rough tools dwelt on the edge of the glacier, and their implements have become buried in the moraines which were forming at many different points during the ice period. Nor can we refuse to admit what this demonstrated fact implies, the great age of man in North America. I have taken, on a former occasion, the sum of 100,000 years as the time that has probably elapsed since the retiring of the glacier from the valleys of the White Mountains, in New Hampshire. This figure was arrived at after a calculation based on the ratio of movement of bodies of ice, and the round number may be considered as an under rather than over estimate. But, at whatever time during the glacial epoch the moraine was formed, in which Dr. Abbott found these implements of early man, it is quite clear that this knowledge alone will not give us the duration of man's existence in North America; for it is certain