200 Henry Clifton Sorhy, LL.B., F.R.8 , F.G.S., etc., 



energy Zirkel continued his labours in the new field of research, and 

 published in succession a number of valuable papers in which minerals 

 like leucite, nepheline, apatite, sphene, etc., were recognised as 

 rock-constituents ; and he found a worthy coadjutor, as enthusiastic 

 as himself, in his brother-in-law, Hermann Vogelsang, whose 

 " Philosophic der Geologie und Mikroskopische Gesteinstudien," 

 published in 1867, and illustrated by descriptions and beautiful 

 drawings of rock-sections, did much towards making the new method 

 of reseai'ch widely known. Investigators like Heinrich Fischer, 

 Tschei'mak, Doelter, Von Lasaulx, and many others took up the 

 work, and numerous papers on the subject were published. In 1873 

 microscopical petrography may be said to have become established as 

 a recognised department of geological science by the publication of 

 two very important works. Zirkel, himself, gave to the world his 

 " Mikroskopische Beschaffenheit der Mineralien und Gesteine," full 

 of very detailed descriptions of the minute characters of minerals and 

 rocks, while Heinrich Rosenbusch, in his "Mikroskopische Physio- 

 graphic der petrographische wichtigen Mineralien," developed the 

 optical principles on which mineral determinations must be made by 

 the aid of the microscope. The publication in 1877 of Rosenbusch's 

 "Mikroskopische Physiographic der massiger Gesteine," and in 1879 

 of Pouque & Michel-Levy's " Mineralogie micrographique des roches 

 eruptives frangaises," with its magnificent atlas of plates, followed by 

 the numerous memoirs of these two authors, and by Lacroix, showed 

 how abundant was the harvest which had sprung from the seed sown 

 by Sorby in 1850. 



It has often been remarked as strange that Sorby did not himself 

 do more in cultivating the field of research which he had so happily 

 discovered. It is true that he never lost his interest in the subject, 

 as was shown by numerous papers on the structure of the sedimentary 

 rocks, on new applications of the microscope, on the determination 

 of the refractive index of minerals, and of the position of the axes of 

 double refraction, and the study of meteorites, slags, and artificially 

 fused rocks. But it was the characteristic of Sorby's mind always to 

 seek for new veins of research rather than to bury himself in mines 

 in which he had already broken grouTid. 



In 1898, when receiving a portrait presented by his fellow- 

 townsmen, he said : " The first thing is to find out some new subject 

 or other, and open out some new line of investigation which is enough 

 to occupy one all one's life. The difiiculty is to avoid discovering 

 new things and at the same time to woi'k up old. I suppose that 

 will go on to the end of the chapter, and I do not know that in doing 

 so I am doing wrong, because possibly it is better to invent new 

 things than to work up old ones thoroughly." These words exactly 

 express the dominant sentiment in Sorby's mind during his whole life. 



I fear that it must be confessed that, in the land of its birth, the 

 new science of microscoj^ical petrography made its way to the front 

 much more slowly than in Germany. Sorby, it is true, almost from 

 the first, found a trusty henchman and doughty champion in David 

 Porbes, who at the Geological Society and elsewhere was always 

 ready to take up the cudgels in Sorby's defence when, as was frequently 



