At head of title: Contributions to cosmogony and the fundamental problems of geology.I. The tidal problem: The former rates of the earth's rotation, by J.C. Chamberlin. The rotation-period of a heterogeneous spheroid, by C.S. Slichter. On the loss of energy by friction of the tides, by W.D. MacMillan. On certain relations among the possible changes in the motions of mutually attracting spheres when disturbed by tidal interactions, by F.R. Moulton. Notes on the possibility of fission of a contracting rotating fluid mass, by F.R. Moulton. The bearing of molecular activity on spontaneous fission in gaseous spheroids, by J.C. Chamberlin.--II. Geophysical theory under the planetesimal hypothesis, by A.C. Lunn.--III. Relations of equilibrium betw...