Prof. Rosenbusch's Work on Petrology

Abstract

OF the great value of Prof. Rosenbusch's work on petrology, so excellently reviewed by Dr. Hatch, to which your correspondent “A. B.” draws attention, there can be no doubt, so far as it is regarded as a storehouse of information; but whether the system of classification proposed therein will not tend to retard rather than to further progress is a question on which I am at present more than doubtful. The two points to which Dr. Hatch and your correspondent draw attention as inherent weaknesses—viz. the “dyke rocks,” and the subdivision of the “effusive rocks” into palæo-volcanic and neo-volcanic—appear to me such serious defects, that to praise a system which largely rests on them is like complimenting a viaduct by saying that it is an excellent viaduct but two of its piers unfortunately have a bad foundation.