To consider the relation of glaciation to other branches of geophysics we must first develop the cause of glaciation; and this will require us to recall some ideas which, though elementary, are fundamental, and it is by keeping fundamental principles in mind that we can build most securely the superstructure.The first requisite for glaciation is the excess of the annual snowfall in a more or less limited region over the melting and dissipation. A mass of snow is thus accumulated which grows in thickness, is gradually converted into ice, and slowly flows away into a region where not only Is the annual snowfall all melted but also the ice which has flowed into it.