Observations on the causes of elevation and subsidence of the earth's crust

Any enquiry into the causes which have produced, and are still producing, mountains and mountain chains cannot be satisfactorily carried out apart from the study of the causes which originally produced the grand irregularities of surface, which primarily determined the original areas of continents and oceans.
In offering any opinion of my own upon the merits or defects of the rival hypotheses assumed by so many eminent physicists to account for elevation and subsidence, I hope it will be conceded that I do so with much diffidence ; for where so many eminent men fail to be satisfied with each other's views on a subject which necessarily rest so largely on arbitrary values for unknown data, it is obvious that any view which I may tend to favour must in my own mind be attended with a large measure of doubt, and on some obscure points my judgment may be suspended entirely. As a novel theory, however, has recently been referred to by Mr. F. Danvers-Power, relating to the elevation of mountain chains, it may be of some interest at this time to enter more fully into the consideration of those hypotheses of causation which have gained the most favour among physicists and geologists.