244 George Ferdinand Becker. 



scale in which to express and compare them, of appro- 

 priate^ means for determining and expressing rigidity, 

 viscosity and other determinative qualities. 



The program was evidently directed to a quantitative 

 study of igneous rocks but did not then reach so far. 

 Nearly ten years were consumed in the preparation of 

 the weapons for the attack, which, from any viewpoint, 

 whether physical or geological, was at that time a hercu- 

 lean task. Then the political upheaval of 1892 intervened 

 to put an end to the undertaking through the familiar 

 Washington method — the discontinuance of appropria- 

 tions. Meanwhile and for some years thereafter Dr. 

 Becker turned to more strictly geological subjects and 

 published many well known monographs : 



Geology of the quicksilver deposits of the Pacific slope (1888), 



The crystalline schists of the Coast Banges of California (1891), 



The interior of the earth (1893), 



Some queries on rock differentiation (1897), 



Fractional crystallization of rocks (1897), 



Report on the geology of the Philippine Islands (1901), 



Present problems of geophysics (1906), 



The age of the earth (1910), 



Isostasy and radioactivity (1915). 



But the necessity for a strict and more comprehensive 

 application of physical law and method to all genetic 

 problems of geology was not for a moment lost sight of 

 and in the "Finite Homogeneous Strain Flow and 

 Rupture of Igneous Rocks" (1893) we recognize a 

 splendid attempt to define and formulate in precise terms 

 some of the relations in the science of "rock mechanics. " 

 This again was a magnificent task of pioneer quality and 

 of extraordinary difficulty, but was not immediately 

 fruitful because clothed in somewhat abstruse mathe- 

 matical form. This paper is destined to exert a 

 considerable influence upon future geological thought 

 (geodynamics). 



In 1900 Dr. Becker was able to reestablish his (geo- 

 physical) Laboratory with the writer as his assistant. 

 The work was resumed substantially where Barus and 

 Hallock had left it in 1892, but with the advantage of 

 more appliances, and proceeded with less interference. 

 The first paper appeared in 1904 (The Isomorphism and 

 Thermal Properties of the Feldspars) and contains an 



