GEOPHYSICAL LABORATORY.* 



Arthur L. Day, Diri;ctor. 



The work which the Geophysical Laboratory has undertaken in determin- 

 ing the relations between the minerals which make up the accessible portion 

 of the earth differs in two essential particulars from the somewhat tentative 

 experiments which have preceded it : ( i ) only those properties have been 

 seriously studied which could be quantitatively measured, and (2) only chem- 

 ically pure minerals made or purified in the laboratory have been used. There 

 are very definite reasons for approaching the great problem of rock form- 

 ation in this way which, to the student of exact science, would seem to be 

 obvious enough, but because these particular questions have rarely been 

 brought into the laboratory for solution the methods of attack still have the 

 appearance of novelty. 



The situation is briefly this : Rock formation, like other physical and 

 chemical phenomena, is the result of certain forces acting upon certain forms 

 of matter. An exact knowledge of rock formation will accordingly depend 

 upon the ability to establish definitely the characteristic properties of these 

 particular forms of matter and to measure the forces which act upon it in 

 each case. The fact that the individual rock-forming minerals do not occur 

 in nature in great purity, and that the active forces are applied over a very 

 great range of conditions and (in nature) over long periods of time, merely 

 encumber the problem with technical difficulties of considerable magnitude; 

 it does not, it must not be allowed to, confuse its analysis. 



Undoubtedly it is true that considerations of this kind have had the effect 

 of retarding and discouraging progress in this field when compared with some 

 of the more accessible fields of research. This happens to have been its 

 history, but it is equally true that no insuperable obstacle now stands in the 

 way of the immediate and general application of modern quantitative methods 

 to establish the relations of the minerals more than of the metals or of inor- 

 ganic salts. Modern chemistry will provide minerals of adequate purity; 

 the conditions, although many and varied, have now been very generally 

 found to be definable and accurately reproducible, and the long periods of 

 time occupied in the growth of natural rocks were perhaps a consequence of 

 the immense mass of participating material and its aggregate energy content 

 rather than a necessary factor in the reactions which took place. Few of the 

 mineral relations so far studied require prohibitive intervals of time for their 

 development. 



* Situated in Washington, D. C. Grant No. 539. $45,000 for geophysical research. 

 (For previous reports on geophysical work see Year Books Nos. 3, 4, 5, 6, and 7.) 



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