The flint implements with which we are concerned as prehistoriaus, and to which we look for evidence of the existence of early man and of the degree of culture to which he had attained, may owe their origin either to the agency of nature or to that of man.

It is of the greatest importance to us that we should be able to distinguish clearly between the products of these two agencies, and the problem of differentiating between them can be approached from two distinct directions. Thus, in dealing with the origin of a given group of implements, we may bring to bear upon the problem our knowledge as to the manner in which flint is fractured and fissured by natural forces, or we may seek for traces of humanity in the method exhibited in the flaking of the implement, the contours of its edges, the evidence of specific design, and the traces of the usage to which the tools have been put.

In approaching the problem from the standpoint of natural forces, we are faced with the fact that our knowledge of the character and the magnitude of the natural forces which have acted, or are acting, upon the flints in question is extremely limited.