REPORT ON GEOPHYSICS l8l 



Dr. James Dewar, Professor of Chemistry in the Royal Institution 

 of Great Britain, is now engaged in testing the strength of rocks at 

 the temperature of liquid air. Already he has reached remarkable 

 (unpublished) results ; but he states that the apparatus and equip- 

 ment at his command are entirely inadequate to carrj^ on experi- 

 mental work on the deformation of rocks at low temperatures on a 

 scale that such work demands in order to give satisfactory results. 

 He says that if a laboratory of geophysics were established the deter- 

 mination of the breaking strength of various rock masses, by com- 

 pressive, tensile, and tortional stresses, should be made at low tem- 

 peratures. He says further that a complete determination of the 

 elastic constants of rocks at different temperatures, under stresses of 

 various kinds, should be made. Professor Dewar states that by the 

 low temperature work upon very small masses of a few varieties of 

 rook in his laboratory he expects to show merely that very impor- 

 tant results can be reached by this line of work, and thus to lay out 

 a great field for extensive work along the same line. Such work as 

 that proposed by Professor Dewar is not provided for anj^where in 

 the world. Such work is especially appropriate to a geophysical 

 laborator5^ 



(4) The Constants of Rocks. — Another set of problems which many 

 geologists desire attacked concern the constants of rocks at various 

 temperatures and pressures, such as their densities, their coefl&cients 

 of expansion, their specific heats, conductivities, etc. The lack of 

 knowledge of these constants, which can certainly be determined by 

 experiment, has stood in the way of the progress of geology in va- 

 rious directions. The need for work along these lines is especially 

 emphasized by Lord Kelvin and Professor Dewar, and is discussed 

 by Dr. Becker in his report of last year. 



Basis of Selection of Problems Suggested. 



In mentioning the foregoing broad lines of investigation I have 

 confined my statements to those which are urgently demanded by 

 many geologists as necessary for the progress of the science. They 

 represent the consensus of opinion of the many geologists with 

 whom I have conferred rather than my own views. I have pur- 

 posely omitted the problems mentioned in the first report of the 

 Advisory Committee for Geophysics that are somewhat more remote 

 from the present pressing problems of the geologist and the student 

 of ore deposits. 



In order to recall some of the lines of work which are not here 



