254 A CENTURY OF SCIENCE 



attention and drew students from all parts of the world 

 to their laboratories, especially to those of Zirkel and 

 Eosenbusch. The great opportunities, facilities, and 

 freedom for work which the German universities had 

 long offered to foreign students of science naturally 

 encouraged this. In France a brilliant school of petrolo- 

 gists, under the able leadership of Michel-Levy and 

 Fouque, had arisen whose work has been continued by 

 Barrois, Lacroix and others, but the rigid structure of 

 the French universities at that period did not permit 

 of the offering of great inducements for the attendance 

 of foreign students. The work of the French petrog- 

 raphers will be noticed in another connection. 



In Great Britain, the home of Sorby, the new science 

 progressed at first slowly, until it was taken up by All- 

 port, Bonney, Judd, Rutley, and others. In 1885 the 

 evidence of the advance that had been made and of the 

 firm basis on which the new science was now placed 

 appeared in TealPs great work, "British Petrography, ' ' 

 which marked an epoch in that country in petrographic 

 publication. This work was of importance also in 

 another direction than that of descriptive petrography, 

 in that it contains valuable suggestions for the applica- 

 tion of the principles of modern physical chemistry in 

 solving the problems of the origin of igneous rocks. In 

 it, as in the publications of Lagorio, we see the passage of 

 the petrographic into the petrologic phase of the science. 



The earliest publication in America of the results of 

 microscopic investigation of rocks that the writer has 

 been able to find is by A. A. Julien and C. E. Wright, 

 chiefly on greenstones and chloritic schists from the 

 iron-bearing regions of upper Michigan. 9 Naturally, it 

 was of a brief and elementary character. In 1874 E. S. 

 Dana read a paper before the American Association for 

 the Advancement of Science on the result of his studies 

 on the "Trap-rocks of the Connecticut valley," an 

 abstract of which was published in this Journal. 10 

 Meanwhile Clarence King, in charge of the 40th Parallel 

 survey, feeling the need of a systematic study of the 

 crystalline rocks which had been encountered, and finding 

 no one in this country prepared to undertake it, had 

 induced Zirkel to give his attention to this task. The 



