926 HENRY CLIFTON SORBY. 



rests was published in the Quarterly Journal Geological Society for 

 1858 (read Dec. 1857) under the title: "On the Microscopical Struc- 

 ture of Crystals, indicating the Origin of Mineral sand Rocks" — a 

 memoir which "though neglected, and even ridiculed at the time, 

 laid the foundations of microscopical petrography — and, in doing so, 

 widened enormously the sphere of influence of mineralogy from which 

 it borrowed so much." 



In the introduction the author summarizes his paper as an attempt 

 to prove that artificial and natural crystalline substances possess 

 microscopic characteristics by which their origin from either aqueous 

 solution or igneous melt can be deduced, and in some cases an approxi- 

 mation made to their rate of formation and to the accompanying- 

 temperature and pressure. The 47 pages of the memoir contain 

 detailed descriptions of many microscopic preparations, illustra,ted 

 by drawings, an account of the methods of preparation, and a dis- 

 cussion of the theoretical application. 



The further development of the new method was at first by German 

 mineralogists, beginning with Dr. Ferdinand Zirkel, with whom Sorby 

 had travelled in 1862 soon becoming an enthusiastic disciple. Zirkel's 

 " Mikroskopische Gesteinstudie" (1863) brought the subject into wide 

 notice and its further development was rapid. 



Thus, while Dr. Sorby gave the start to the new science, he left its 

 further development to others, devoting himself to many other 

 problems of geological science, and to other sciences, so that almost 

 250 papers represented his scientific activity, as continued over sixty 

 years, and until his death. He was elected Foreign Honorary Mem- 

 ber of this Academy in 1892. 



A detailed account of his life and activities has been given by the 

 late Professor J. W. Judd in the Geological Magazine for 1908 and in 

 the Mineralogical Magazine for the same year, from which the present 

 memoir is mainly an abstract. 



John E. Wolff. 



