Dr. G. T. Prior — Progress of Mineralogy. 11 



soon able to announce the discovery in them of several new species, 

 one of which, the sulphide of calcium, oldhamite, must have been 

 formed under conditions very different from those which prevail on 

 the earth's surface. 



Shortly before this time the sciences of both geology and 

 mineralogy, having passed through times of stress, had been placed 

 upon the sure foundations on which the present superstructures 

 have been built. 



In the case of geology, starting with the broad conception of the 

 earth's crust as made up of rocks, the founders of the science, after 

 a prolonged and bitter struggle between "neptunists" and 

 "plutonists", had at length learned, by accepting truth from both 

 sides, to distinguish clearly between two main types of rocks, the 

 sedimentary, owing their origin to superficial agencies acting on 

 the earth's surface, and the igneous, resulting from deep-seated 

 agencies acting from the earth's interior. Guided by the 

 principle that the present is the key to the past, which had been 

 enunciated by Hutton and enforced by the teaching of Lyell, the 

 geologist soon saw spread before him the ordered sequence of the 

 sedimentary rocks, with their fossils giving a record, imperfect 

 though it might be, of the gradual evolution of plant and animal life 

 down the ages. Along these lines geology, on its stratigraphical and 

 palaeontological side, could develop, and has indeed continued to 

 develop up to the present day, without feeling the necessity for 

 paying a great amount of attention to the mineral composition of the 

 rocks with which it dealt. The investigation of the igneous rocks, 

 however, presented a different problem. After the main facts of the 

 processes of vulcanism and igneous intrusion had been grasped, 

 further pxogress might have been barred for a long time but for such 

 work as that of Sorby in directing attention to the use of the 

 microscope in determining the mineral composition of rocks. The 

 branch of microscopical petrography thus initiated, and developed 

 later by the exertions of Zirkel, Kosenbusch, and Teall, forms the 

 connecting link between geology and mineralogy. As has been 

 rightly said, mineralogy is the chief buttress on which the science of 

 rocks, or petrology, rests ; for to attempt to study rocks without 

 minerals would be like trying to investigate and classify a group of 

 animals by their external features with little reference to their 

 internal anatomy. 



Into an error of this kind mineralogy, indeed, had been in danger 

 of falling in the earlier stages of its career. Under the influence of 

 Mobs an attempt had been made to restrict the study of minerals to 

 their natural history characters, such as ci-ystalline form, hardness, and 

 specific gravity, to the exclusion of the chemical properties. Mineralogy 

 without elements would thus have been in a state comparable to 

 that of geology without minerals. No branch of science, however, 

 as pointed out by Sir Henry Miers in a recent lecture on this same 

 subject before the Chemical Society, can afford to maintain a position 

 of splendid isolation for long. Sooner or later in its development 

 there comes a stage when for any further advance it becomes 

 necessary to seek the aid of other sciences in order to elucidate the 



