It is true that in various parts of the world, during the past few years, human bones have been discovered in connection with the bones of the fossil mammalia; but they were generally found in caves or in lime-deposits, where they might have been dropped or swept in by currents of water, or inserted in more modern periods, and yet covered with the same deposit as the more ancient relics.  Geologists have uniformly reasoned on the a priori improbability of these being fossil bones, and have somewhat strained the evidence—­as some distinguished savans[A] now believe—­against the theory of a great human antiquity.

[Footnote A:  Pictet.]

And yet the “negative evidence” against the existence of the fossil man was open to many doubts.  The records of geology are notoriously imperfect.  We probably read but a few leaves of a mighty library of volumes.  Moreover, the last ages preceding the present period were witnesses of a series of changes and slowly acting agencies of destruction, from which man may have in general escaped.  We have reason to believe that during long periods of time the land was gradually elevated and subject to oscillations, so that the courses of rivers and the beds of lakes were disturbed, and even the bottom of the ocean was raised.  The results were the inundation of some countries, and the pouring of great currents of water over others, wearing down the hills and depositing in the course of ages the regular layers of gravel, sand, and marl, which now cover so large a part of Europe.  This was still further followed by a period in which the temperature of the earth was lowered, and ice and glaciers had perhaps a part in forming the present surface of the northern hemisphere.  During the first period, which may be called the “Quaternary Period,"[B] the mighty animals lived whose bones are now found in caverns, or under the slowly deposited sediment of the waters, or preserved in bog,—­the mammoth, and rhinoceros, and elk, and bear, and elephant, as well as many others of extinct species.

[Footnote B:  We should bear in mind that the Quaternary or Diluvian Period, however ancient in point of time, has no clearly distinguishing line of separation from the present period.  The great difference lies in the extinction of certain species of animals, which lived then, whose destruction may be due both to gradual changes of climate and to man.—­PICTET.]

We may suppose, that, if man did exist during these convulsions and inundations, his superior intelligence would enable him to escape the fate of the animals that were submerged,—­or that, if his few burial-places were invaded by the waters, his remains are now completely covered by marine deposits under the ocean.  If, however, in his barbarian condition, he had fashioned implements of any hard material, and especially if, as do the savages of the present family of man, he had accidentally deposited them, or had buried them with the dead in mighty mounds, the invading waters might well sweep them together from their place and deposit them almost in mass, in situations where the eddies should leave their gravel and sand.[C]