The relations of isostatic readjustment with mining geology or with other applications of the science to problems in professional practice are those of large, general character, of fundamental conceptions, and of great first causes, rather than of special service in particular cases. When an ore body is cut off by a fault and the mining geologist has to decide what to do next in order to find the missing part, the conceptions based on isostasy are not of immediate help; but if in his daily work the thoughts of the mining geologist turn to the cause of the faults with which he has to deal, isostatic readjustment must of necessity come into his field of view in a fundamental way. In responding to the request of Mr. Bowie to add a few pages of reflections on these questions to the symposium, I am compelled by the very nature . . .