The question of the geological age of the earth has been of late very prominently before the minds both of geologists and physicists. There is no occasion to take up time by giving a sketch of the late history of the discussion. I beg leave simply to point out some considerations which seem to lessen considerably the weight of the physical objections to the great extent of geological time. Let us observe before proceeding further that we do not wish to avoid wholesome restriction of geological time. It seems to me that it adds greatly to the interest of geological investigation to know that we have not a wilderness of possibility before us as to the length of time and the consequent deliberateness of geological operations.