ADVISORY COMMITTEE ON GEOPHYSICS 47 



nature of igneous solutions, their chemical affinities, their ioniza- 

 tion, latent heat, eutectic properties, etc. A special branch of this 

 subject, but one of the most important, is the study of aquo-igneous 

 fusion and the solutions resulting from it. The study of eutectic 

 mixtures, including those into which the hydroxyl enters as a com- 

 ponent, should lead to a classification of massive rocks on a new 

 basis. Vulcanism also demands a study of the viscosity and diffus- 

 ivity of solutions, especially of magmas, and of the relations which 

 must subsist between them. The results obtained should be de- 

 terminative with reference to the theory of the so-called " differen- 

 tiation " of rock magmas. Diffusivity is inversely proportional 

 to some function of viscosity, and there is some probability that 

 this function is the square. Preparations are now in progress to 

 test these relations in my laboratory bj^ novel methods. 



The cause of the extrusion or the intrusion of magmas is un- 

 known. I am of the opinion at present that its origin is the elastic 

 pressure of solid masses upon materials deprived of their rigidity by 

 fusion. This may at least serve as a starting point for investiga- 

 tion. It appears then that vulcanism is probably allied to orogeny 

 in an intimate manner. 



Its study will require at least one additional physicist devoted to 

 researches on the physical properties of solutions and of a physical 

 chemist to undertake the more purely chemical properties of 

 magmas. 



J. Necessity for Organized Research in Geophysics. — This brief 

 outline of the possibilities of systematic investigation in three of 

 the most important problems of geophysics appears to me to 

 justify the opinion that a special corps of investigators, with 

 special laboratory facilities and under a single directorship, should 

 be devoted to the study of geophysics. In my opinion, it would be 

 beyond the power of any one man to co-ordinate the various 

 branches of the work of a geophysical laboratory, while paying due 

 regard to the needs of geological science, and at the same time to 

 superintend any more extensive scheme of physical research. To 

 be successful the work must be organized with reference to its spe- 

 cial character, and even then the task will severely tax the best 

 corps of men which can be enlisted. On the other hand, it is diffi- 

 cult to imagine contributions to general phj'sics of more funda- 

 mental importance than those which would ensue from the success- 

 ful prosecution of these geophysical researches. 



