The fact has thus been proved that a race of men lived upon the earth at the epoch settled by the geological age of these strata--that is, during the quaternary epoch. When this class of evidence of man's presence--that is, the vestiges of his primitive industry--fails us, a state of things, however, which comparatively seldom occurs, his existence is sometimes revealed by the presence of human bones buried in the earth and preserved through long ages by means of the deposits of calcareous salts which have petrified or rather _fossilised_ them. Sometimes, in fact, the remains of human bones have been found in quaternary rocks, which are, consequently, considerably anterior to those of the present geological epoch. This means of proof is, however, more difficult to bring forward than the preceding class of evidence; because human bones are very liable to decay when they are buried at shallow depths, and require for any length of preservation a concurrence of circumstances which is but rarely met with; because also the tribes of primitive man often burnt their dead bodies; and, lastly, because the human race then formed but a very scanty population. Another excellent proof, which demonstrates the existence of man at a geological epoch anterior to the present era, is to be deduced from the intermixture of human bones with those of antediluvian animals. It is evident that if we meet with the bones of the mammoth, the cave-bear, the cave-tiger, &c.,--animals which lived only in the quaternary epoch and are now extinct--in conjunction with the bones of man or the relics of his industry, such as weapons, implements, utensils, &c., we can assert with some degree of certainty that our species was contemporaneous with the above-named animals. Now this intermixture has often been met with under the ground in caves, or deeply buried in the earth. These form the various kinds of proof which have been made use of to establish the fact of man's presence upon the earth during the quaternary epoch. We will now give a brief recital of the principal investigations which have contributed to the knowledge on which is based the newly-formed science which treats of the practical starting-point of mankind. Palæontology, as a science, does not count more than half a century of existence. We scarcely seem, indeed, to have raised more than one corner of the veil which covers the relics of an extinct world; as yet, for instance, we know absolutely nothing of all that sleeps buried in the depths of the earth lying under the basin of the sea. It need not, therefore, afford any great ground for surprise that so long a time elapsed before human bones or the vestiges of the primitive industry of man were discovered in the quaternary rocks. This negative result, however, always constituted the chief objection against the very early origin of our species.