Page:Popular Science Monthly Volume 1.djvu/121

Rh being, representing man, then flourished, some signs of his existence could hardly have escaped unnoticed, in the shape of implements of stone or metal, more frequent and more durable than the osseous remains of any of the mammalia."

It is true that few of our existing species, or even genera, have as yet been found in miocene strata; but if man constitutes a separate family of mammalia, as he does in the opinion of the highest authorities, then, according to all paleontological analogies, he must have had representatives in miocene times. We need not, however, expect to find the proofs in Europe; our nearest relatives in the animal kingdom are confined to hot, almost to tropical climates, and it is in such countries that we are most likely to find the earliest traces of the human race.

M. Morlot has made some interesting calculations respecting the age of geological formations in Switzerland. The torrent of the Tinière, at the point where it falls into the Lake of Geneva, near Villeneuve, has gradually built up a cone of gravel and alluvium. In the formation of the railway this cone has been bisected for a length of 1,000 feet, and to a depth, in the central part, of about 32 feet 6 inches above the level of the railway. The section of the cone thus obtained shows a very regular structure, which proves that its formation was gradual. It is composed of the same materials (sand, gravel, and large blocks) as those which are even now brought down by the stream. The amount of detritus does, indeed, differ considerably from year to year, but in the long run the differences compensate for one another, so that, when considering long periods, and the structure of the whole mass, the influences of the temporary variations, which arise from meteorological causes, altogether disappear, and need not, therefore, be taken into account. M. Morlot's estimates assign about 6,000 years for the formation of the lower layer of vegetable soil, and 10,000 years for that of the whole existing cone. But above this cone is another, which was formed when the lake stood at a higher level than at present, and which M. Morlot refers to the period of the river drift gravels. This drift age cone is about twelve times as large as that now forming, and would appear, therefore, on the same data, to indicate an antiquity of more than 100,000 years.

Again, it will be remembered that, side by side with the remains of Arctic animals, have been found others indicating a warm climate, such for instance as the hippopotamus. This fact, which has always hitherto been felt as a difficulty, is at once explained by the suggestion of a change every 10,000 or 11,000 years, from a high to a low temperature, and vice versa. But a period of 10,000 years, long as it may appear to us, is very little from a geological point of view. We can thus understand how the remains of the hippopotamus and the bones of the musk ox come to be found together in England and in France. The very same geological conditions which fitted our valleys for the