In the preparation of this paper, the writer has been assisted in many ways. It is a pleasure to record thanks due to Cordell Durrell, a graduate student of the University of California, for his able assistance in the field, and for preparing the outlines of the block diagrams (Figs. 3 and 4). Unfortunately, the excellent advance sheet of the Newberry Crater quadrangle was not available for field-work, but the reconnaissance maps of the Forest Service were supplemented, in part, by detailed plans kindly loaned by George Conklin, of the Shevlin-Hixon Lumber Company. The writer is also glad to acknowledge his indebtedness to Professor C. A. Anderson, not only for a critical review of the manuscript, but also for many discussions, all the more welcome in view of the fact that he has lately commenced a detailed study of the Medicine Lake Highlands of northern California, which bear many . . .