Page:Popular Science Monthly Volume 48.djvu/32

22 mention a few instances. In 1715 a flint knife, now in the British Museum, was found imbedded in gravel with the tooth of an extinct species of elephant, near Gray's Inn Lane, London, thus marking the extreme antiquity of flint instruments. In 1797 flint hatchets were found in Suffolk, and in 1847 flint instruments at Abbeville. In 1858 Sir Charles Lyell found others in the valley of Somme in Picardy. Flint instruments have been found in caves all over the earth, mixed with bones of animals that lived before, during, and after the Glacial period. They can be more or less classified according to their form and finish. We believe that in all instances flint instruments have been found with what are supposed to be the earliest skeletons of mankind; moreover, the oldest type of flint instrument has been found with the skeleton of man.

The difficulty now is to assign a period to the earliest type of flint instrument. If this can be done, the period in which man first appeared on the earth can be more precisely ascertained, and this in two ways—either by finding these flint instruments beneath certain strata which can be assigned to certain periods by geologists, or by finding them with the bones of certain animals the period of whose extinction is also approximately known. This only is certain: that the bones of extinct species of animals, extinct yet still represented by later races, have been found in these and other caverns with those of man and with flint instruments. These bones are those of mammalia of the Miocene, Pliocene, and Pleistocene periods. Secondly, the caverns in which these human bones have often been found have, we believe, been always in the Secondary and Lower Cretaceous rocks, though this does not, of course, show that man was in existence immediately after the formation of these rocks, but merely that they were the most accessible and convenient for him in which to live or be buried, for many of the skeletons that have been discovered seem to have been carefully buried by others. The alluvial deposits, formed by the action of water, which actually contain man's remains, belong to a more modern era than the newest stage of the Tertiary epoch and are within the Post-tertiary series, in the Pleistocene, Glacial, or Bowlderdrift period, as it is variously