GEOPHYSICAL LABORATORY 285 



earth-forming oxides. The petrographic laboratory has 

 been available for the comparison of synthetic laboratory 

 products with the corresponding natural minerals. 



It has also proved entirely practicable to extend the 

 same methods of research to some of the principal ore 

 minerals such as the sulphides of copper. Other infor- 

 mation which is certain to be of ultimate economic value 

 has also come out of the thorough study of the silicates, 

 which are basic materials for the vast variety of indus- 

 tries which are classed under the name of ceramic indus- 

 tries. The best example of this is the facility with which 

 the experience and the personnel of the laboratory has 

 been adapted to the very important problem of manufac- 

 turing an adequate supply of optical glass for the needs 

 of the United States in the present war. 



It has further been possible to show within the last two 

 years that rock formation in which volatile ingredients 

 play a necessary and determining part can be completely 

 studied in the laboratory with as much precision as 

 though all the components were solids or liquids. 



Along with the laboratory work on the formation of 

 minerals and rocks has gone an increasing amount of field 

 work on the activities of accessible volcanoes, such as 

 Kilauea and Vesuvius, where the fusion and recrystal- 

 lization of rocks on a large scale can be observed and 

 studied. 



There was once a time when the confidence of the lab- 

 oratory in the capacity of physics and chemistry to solve 

 geological problems was not shared by all geologists. 

 There were some who were inclined to view with consid- 

 erable apprehension the vast ramifications and com- 

 plications of natural rock formation as a problem 

 impossible of adequate solution in the laboratory. It is, 

 therefore, a matter of satisfaction to all those who have 

 participated in these efforts to see the evidences of this 

 apprehension disappearing gradually as the work has 

 progressed. A careful appraisement of the situation 

 to-day, after ten years of activity, reveals the fact that 

 the tangible grounds for anxiety about the accessibility 

 of the problems which were confronted at first are now 

 for the most part dissipated. 



It will not be possible to review in detail the lines of 



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