more general homogeneity in large masses, and their lack of sharply defined bands or layers of varying composition. The fact that the minerals have always crystallized to form medium to coarse-grained rocks shows that these rocks solidified under deep-seated conditions, since it is well known that surface flows (lavas) are much finer grained commonly with more or less of the rock not crystallized at all. Slow cooling under great pressure favors more complete crystallization with growth of larger crystals. As we have just learned, the very character and structure of the Archeozoic rocks now exposed to view show conclusively that they were formerly deeply buried, and the inference is perfectly plain that the overlying rock materials were removed by erosion. Profound erosion of any land mass means that the land must have stood well above sea level, and thus we come to the important conclusion that the great mass of Archeozoic rocks (both strata and igneous rocks) were upraised well above sea level. Just when the uplift occurred cannot be positively stated, but in every region where the matter has been studied it took place before the strata of the next geological era began to deposit as shown by the fact that such later strata rest upon the profoundly eroded surface of the Archeozoic rocks. Such an erosion surface, called an "unconformity," marks a gap in the geological record of the district where it occurs. There is much to support the view that the uplift was concomitant with the great igneous intrusions, especially the granite. It is reasonable to believe that the same great force which caused the welling up of such tremendous bodies of liquid rock into the earth's crust might easily have caused a decided uplift of a whole large region, but even so the process must have been geologically slow. In regard to the height of those ancient lands, the character of the topography, and the drainage lines we are as yet utterly in the dark. The fact that many thousands of feet in thickness of materials were removed by erosion to expose the once deeply buried rocks, does not necessarily imply that the lands at any time had great height, because it is possible that while elevation slowly progressed, much material was steadily removed by erosion. In the light of our knowledge of the origin and growth of mountain ranges of later time there is little doubt that at least some of the Archeozoic lands were raised to such mountain heights.