EISE OF PETROLOGY AS A SCIENCE 263 



On the theoretical side also, where petrology passes 

 into geology, the investigator of to-day will find a mass 

 of most useful and accurate data well discussed in the 

 modern representative of Bischof 's Chemical Geology 

 Clarke's Data of Geochemistry. 38 The advance on the 

 chemical side, therefore, has been quite commensurate 

 with that in the microscope as an instrument, and in the 

 results obtained by it. 



PJiysico- Chemical Work, 



The study of geological results by experimental 

 methods, which should gain information concerning the 

 processes by which those results are caused, and the con- 

 ditions under which they operate, has been from the 

 earliest days of the developing science recognized as 

 most important, and the record of the literature shows 

 considerable was done in this direction. Experimental 

 work in modern petrology may, however, be considered 

 to date from 1882 when Fouque and Michel-Levy 39 pub- 

 lished the results of their extensive researches on the 

 synthesis of minerals and rocks by pyrogenous methods. 

 The brilliant experiments of the French petrologists at 

 once attracted attention, and since that time a consid- 

 erable volume of valuable work has been done in this 

 field by a number of men, among whom may be men- 

 tioned Morozewicz, 40 Doelter, 41 Tamman, 42 and Meunier. 43 

 As this work continued the results of the rapid advances 

 made in physical chemistry began to be applied in this 

 field with increasing value. To J. H, L. Vogt we owe a 

 valuable series of papers, 44 in which the formation of 

 minerals and rocks from magmas is treated from this 

 standpoint. Most important of all for the future of 

 petrology has been the founding in Washington of the 

 splendid research institution, the Carnegie Geophysical 

 Laboratory, under the leadership of Dr. A. L. Day with 

 its corps of trained physicists, chemists and petrologists, 

 devoted to the solving of the problems which the progress 

 of geological science raises. The publications of this 

 institution (many of them published in the Journal) are 

 too numerous to be mentioned here; many of them 

 treat successfully of matters of the greatest importance 

 in petrology. This is an earnest of what we may hope in 



