ADVISORY COMMITTED ON GEOPHYSICS 33 



mutual separation and the reduction of rotations, but just how 

 much this may signify in the history of the past and of the future 

 requires a new and much broader inquiry than it has yet received, 

 checked by independent lines of evidence. The question whether 

 the earth is now bodily deformed by tidal stress requires experi- 

 mental demonstration or overthrow, as an essential factor in this 

 problem. This would test the effective rigidity of the earth, and 

 give aid to the solution of other problems. The motion of the 

 moon and the precession of the equinoxes perhaps give lines of ap- 

 proach to the distribution of mass in the earth, and hence to its 

 internal density, etc. The origin of the size, form, constitution, 

 motions and relations of the earth are locked up with the origin of 

 the solar system, and, in general, the deeper terrestrial questions 

 lead out in the end into the realm of cosmology, where the studies of 

 the geologist, astronomer, physicist and chemist blend. Geophysi- 

 cal stud)^ must here borrow much from astronomy, but it should 

 make an equivalent return, for the phenomena of the earth are most 

 important factors in cosmology. Any great laboratory of geo- 

 phj^sics should do its part in this vast field. 



(d) Some of the more specific problems nozv pressing for solution. 



1 . Experiments to demonstrate the diathermacy of the atmosphere 

 and its dependence upon its several constituents, their relations 

 to each other, their ionization, their nucleation, and their other 

 states. 



2. Determinations of the gases held in magmas, rocks and mete- 

 orites, and the states in which they are held, together with inquiry 

 into the powers of selection and absorption of gases by rocks under 

 ordinary and unusual conditions. 



3. Determinations of the functions of the ocean as a reservoir of 

 atmospheric material, involving a study of the relations of its saline 

 constituents to the absorption and release of atmospheric constitu- 

 ents, the relations of temperature and pressure to such absorption 

 and release, as also the functions of vegetable and animal life in the 

 process. 



4. Experiments to determine the physical chemistry of natural 

 solutions and precipitates ; one important purpose being to furnish 

 a basis for a more comprehensive science of ore deposits. 



5 . The artificial alteration and recrystallization of minerals under 

 different chemical and physical conditions, in imitation and eluci- 

 dation of the natural alteration of minerals. 



