GEOPHYSICAL LABORATORY.^ 



Arthur L. Day, Director. 



This report, the fifteenth in annual succession since the founding of 

 the Geophysical Laboratory, may properly take note of a gradual 

 change in the outlook over our field of research as time goes on and 

 experience increases. When it was first proposed to study quanti- 

 tatively, in the laboratory, the manner of formation of the igneous 

 rocks, the questions which arose in the minds of those interested were 

 mainly questions of practicability and not of desirability or of the scope 

 of the task. This had long been deemed to be not only a desirable but 

 an indispensable chapter in the history of the earth, which had hitherto 

 to be viewed from a distance, with the telescope of speculation, as it 

 were, because of the physical difficulties of near approach. Neither 

 was any attempt made to define its proper scope. A telescopic view 

 of a new field of activity does not at once reveal boundaries nor sug- 

 gest limitations. Even the prefix supplied to create the names 

 ''Geophysics" or "Geochemistry" suggests no limitation upon the 

 ordinary use of the terms physics and chemistry such as is implied in 

 ''Astrophysics." 



The real difficulty which presented itself persistently in the early 

 consideration of the project was one of practicability. Could such a 

 field of research, which in the minds of geologists comprehended the 

 most majestic of terrestrial phenomena, be brought into the laboratory 

 with hope of finding successful elucidation there? Could an attack 

 from the experimental side yield quantitative relations, or would it 

 provide no more than feebler imitations of natural phenomena, power- 

 less alike for analysis or prediction? Would it be possible to make a 

 competent study of all the processes of rock formation, even with all the 

 available resources of physics and chemistry? 



The reactions in igneous rocks might be expected to occur almost 

 exclusively in a region of temperatures so high that even their measure- 

 ment could not then be regarded as certain. Would it, then, prove 

 practicable to detect and measure transfers or transformations of 

 energy at those high temperatures, to segregate for purposes of identi- 

 fication the participating components in any transfer of energy in a 

 silicate solution, to determine the heat of fusion, the degree of viscosity, 

 the power of convection, the separation of the products of early 

 crystallization within the magma under the action of gravity or tem- 

 perature change or of mobile volatile components, or, indeed, to de- 

 termine when a condition of equilibrium capable of precise definition 

 had been reached? Unless it should prove practicable to establish 

 and recognize a state of equilibrium, there was little hope of definition 



^Situated in Washington, District of Columbia. 



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