FUNDAMENTAL PROBLEMS OF GEOLOGY. 



By T. C. Chamberlin. 



Sir : I have the honor to submit herewith a report of progress on 

 the work done under Grant No. 1 1 5 , in continuation of Grant No. 3 1 . 



For the general scheme of the work I beg to refer to my previous 

 report (Year Book No. 2, pp. 261-270). The work upon which I 

 have been engaged during the current year has lain wholly within 

 the lines there sketched and chiefly within the constructive phases 

 of the scheme. On the critical side, however, I have reviewed the 

 tests previously applied to the Laplacian and allied hypotheses of 

 the origin of the earth, but have added little to them. The cogency 

 of their adverse bearings seems to be in no wa)^ diminished by 

 reflection or reconsideration. 



I have developed into more definite terms several phases of the 

 meteoritic hypotheses of the earth's origin of the type advocated by 

 lyockyer and Darwin ; that is, the type in which the meteorites are 

 supposed to be assembled as a swarm, the individual meteorites 

 moving to and fro and frequently colliding after the manner of the 

 molecules of a gas, a constitution brought into clear definition by the 

 classic paper of Darwin, " On the Mechanical Conditions of Swarms 

 of Meteorites and on Theories of Cosmogony. ' ' * Working upon 

 the results reached by Darwin, it has not appeared probable that at 

 a position so deep in the postulated swarm as that at which the earth 

 should have been formed, a passage from the quasi-gaseous into the 

 true gaseous condition could have been escaped, because of the fre- 

 quency and violence of the collisions and the consequent high temper- 

 ature ; and hence, so far as the origin of the earth is concerned, this 

 phase of the meteoritic hypothesis seems to become identical with the 

 gaseous or L,aplacian hypothesis and to be obnoxious to most of 

 the objections to that hypothesis that arise from the kinetic action 

 of the gases and from the relations of mass and momenta, as brought 

 out in the previous studies by Dr. Moulton and myself. 



Studies in the line of meteoritic swarms have usually started with 

 the swarms organized, and have not seriously considered whether 

 such swarms would be likely to arise. There is no positive proof 

 of the present existence of meteoritic swarms with such a dynamic 

 organization. There are, to be sure, spectroscopic and other grounds 



*PKil. Trans. Royal Society, 1SS8. 



195 



