In view of the fact that one or two friends have spoken to me of this paper as propounding original theories, a word of personal explanation may not be out of place. I claim no such originality. It is true the main outlines of this theory of igneous phenomena came into my consciousness as the result apparently of my own thinking when, in college days, I was convinced by Darwin’s paper in Thomson’s and Tait’s “Natural Philosophy ” that the earth must be regarded as rigid; but in the intervening years I found in reading along the suggested lines that almost every point had been thought out before me. Meanwhile the facts have been marshalling themselves in my mind around this theory, and in this connection I must acknowledge obligation to Neumayr’s “Erdgeschichte” and to writings and conversations with numerous teachers and friends.
Nearly five years ago there was . . .