DURING the last few years there has appeared a regular flood of literature, both abstrusely technical and more or less popular, dealing with such questions as the origin and form of the earth as a whole, the stages of its history, the formation of its crust, the building of land and sea, the uprise of mountain ranges, the form and displacement of continents, the physics and mechanics of vulcanicity, and a large number of other phenomena of cosmical and geodetical nature, as well as much speculation as to the birth of the moon and its relation to the earth. These subjects have been treated from every possible point of view - astronomical., mathematical/ physical, chemical, and geological. It might seem, therefore, unnecessary to add to the number of writings in this much occupied field. Nevertheless, to a geologist there seem, to be certain aspects of the case that have not yet been quite sufficiently co-ordinated and considered in their mutual relations. Let this be the excuse for the following somewhat theoretical and speculative discussion.