between certain of the layers of glacial materials in Australia, South Africa, and Brazil. During much of Permian time the climate was arid over large areas as, for example, much of the western interior of the United States, from Ireland to central Germany, and in eastern Russia, as proved by great deposits of salt, gypsum, and red sediments. During late Permian time the greatest salt beds in the world were deposited in northern Germany, a well near Berlin having penetrated a practically solid body of salt associated with certain potash and magnesia salts to a depth of about 4,000 feet without reaching the bottom. The occurrence of some coal beds, especially in the earlier Permian rocks shows that, temporarily at least, climatic conditions must have favored luxurious growths of coal-forming plants in South Africa, Brazil, Australia, and our own Appalachian district. From the above facts we see that the Permian represents a remarkable combination of very extensive glaciation, widespread aridity, and warmth and moisture favorable to prolific plant growth all in a single period of geologic time. The Permian period, and, therefore, the great Paleozoic era, was brought to a close by one of the most profound physical disturbances in the known history of North America. This has been called the Appalachian Revolution because at that time the Appalachian Mountain range was born out of the sea by folding and upheaval of the strata. In fact, "the Appalachian Revolution was one of the most critical periods in the history of the earth, and may have been the greatest of them all in its results." (C. Schuchert). Mountains were brought forth in all the continents, including Australia. All of the mountains which were formed late in the Paleozoic have since been profoundly affected by erosion, and the only ones (e.g., Appalachians) which now show considerable altitudes are those which have been rejuvenated by relatively (geologically) recent earth movements. We shall now turn our attention to the origin of the Appalachian Range. All through the vast time (probably fully 20,000,000 years) of the Paleozoic era a large land mass was remarkably persistent along the eastern side of North America. This land, which has been called "Appalachia," had its western boundary approximately along the eastern border of the sites of the Appalachian Range and the western part of New England. It extended east of the present coast line at least to the border of the continental shelf from 100 to 200 miles out. Concerning the actual altitude and topography of Appalachia we know little or nothing, but the tremendous quantities of sediment derived from its erosion show that it was high enough during nearly all of its history to undergo vigorous erosion.