ANNIVERSARY ADDRESS OE THE PRESIDENT. 6 1 



of species, has endowed this branch of natural science with the 

 transforming- conception of Evolution. 



Now these two causes which have done so much for Biology are 

 already working out the regeneration of Mineralogy ; and I doubt 

 not that in due time the fruits brought forth by the latter science 

 will be equally satisfactory with those of the former. 



The application of the microscope to the study of minerals has 

 proved less easy than in the case of animal and vegetable structures. 

 More than a century ago, it is true, several French geologists 

 employed the method of crushing a rock, and of picking out from its 

 powder the several minerals of which it was composed, for micro- 

 scopic study ; and in 1816, Cordier endeavoured, by systematizing 

 the methods followed by his predecessors, Daubenton, Dolomieu, 

 Fleurian, and others, to elaborate a scheme for the mineralogical 

 analysis of rocks by the aid of the microscope. In recent years the 

 French geologists, with MM. Eouque and Michel Levy at their 

 head, have shown how, by the employment of the electro-magnet, of 

 fluids of high density, and of various chemical reagents, this work 

 of isolating the several minerals of a rock for microscopic study or 

 chemical analysis may be greatly facilitated. 



But the great drawback to this method of microscopic study of 

 rocks, as devised in France, was found in the circumstance that it 

 began by destroying the rock as a whole, and hopelessly obliterating 

 the relations of its mineralogical constituents. Delesse and other 

 observers, it is true, succeeded in obviating this difficulty, to some 

 extent, by studying the structure of rocks as seen in polished surfaces 

 under the microscope by reflected light. 



The greatest step in advance in connexion with the microscopic 

 study of rocks was undoubtedly made, however, when it was shown 

 that transparent sections of minerals, rocks, and fossils can be 

 prepared, comparable to those so constantly employed by biologists 

 in their researches. William Nicol, of Edinburgh, was the first to 

 discover, in the year 1827, how the mechanical difficulties in the 

 way of the preparation of such sections could be surmounted ; while 

 Mr. Sorby, in a memorable communication to this Society, in 1858, 

 showed us the first-fruits of the wonderful harvest of results to be 

 obtained by the employment of this method. 



But if the birthplace of the one method of microscopic study of 

 rocks was France, and of the other Britain, it must be confessed 

 that a large part of the merit of developing and improving these 

 methods of inquiry is due to the Germans. To the labours of the 



