ficial, whatever conclusions it leads to. In this field he stood forth as the chief exponent of doctrines maintained against strong and widespread opposition, forced into recognition and partial acceptance by the sheer vigor and energy with which he defended them, and the learning and skill with which he marshalled a tremendous array of evidence in their support. I, who disbelieve these views and have taken some share in combating them, can well afford to honor the ability and industry with which they were defended. Heterodoxy is of the life of scientific doctrine, the surest indication of its vigor and progressiveness. Only in decadence will our theories degenerate into a "body of geologic dogma," admitted to universal belief with universal indifference.
