228 L. V. Pirsson — Rise of Petrology as a Science. 



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 

 result of this labor appeared in 1876 in a fine volume 11 

 which attracted great attention. In the same year 

 appeared also petrographical papers by J. H. Caswell, 12 

 E. S. Dana 13 and G. W. Hawes. 14 The latter devoted 

 himself almost entirely to this field of research and may 

 thus, perhaps, be termed the earliest of the petrog- 

 raphers in this country. His work, "The Mineralogy 

 and Lithology of New Hampshire," issued in 1878 as one 

 of the reports of the State Survey under Prof. C. H. 

 Hitchcock, was the first considerable memoir by an 

 American. This was followed by various papers, one on 

 the "Albany Granite and its contact phenomena," 15 

 being of especial interest as one of the earliest studies of 

 a contact zone, and in the fullness of methods employed 

 in attacking the problem forecasting the change to 

 the petrology era. 



During the ten years following, or from 1880 to 1890, 

 the new science of petrography flourished and grew 

 exceedingly. Many young geologists abroad devoted 



