The fullest credit must be given to our members, Mr. Reid Moir, F.G.S., and Mr. S. Hazzledine Warren, F.G.S. (and others also) for their efforts to solve this problem by experiment. This is obviously the right line to adopt, but, after all, experiments (including my own, for I have been experimenting for years on similar lines) are only proof that (given suitable conditions) the sharp edges of split flints will chip under “Force,” whether this is applied by Nature or Man. Experiments can prove the difference between the results of the forces of “Percussion” and “Pressure”: but it is doubtful, in my opinion, if it can be proved by experiments whether Nature or Man has applied the force, as the same forces are used by both Nature and Man, the only difference being the intensity with which the force has been used and the way that force has been applied.