Very different views have been held as to the precise condition of the continents in the Glacial Age, though all agree in the prevalence of cold and the action of ice, and in the fact of a great submergence at one or more stages of the period. My own conclusions, which I have advocated elsewhere,[84] and which are based on extensive study of the northern parts of America, where the deposits of this age are more widely developed than elsewhere, are that there was one great subsidence, leading to a condition in which the lower levels of the continents were covered with ice-laden water and the higher regions were occupied with permanent snow and glaciers. This submergence went on till even high mountains 4,000 feet or more in elevation were under water. Then there was a gradual though intermittent elevation, during which the climate became ameliorated, and lastly there was a condition in which the land of the northern hemisphere stood higher than at present, and which immediately preceded the modern period. As these conditions have great significance in relation to the appearance of man, I have tabulated them for reference as they occur in Scandinavia, Great Britain, and North America. The so-called “Interglacial Periods” of some geologists are in reality local results of the stages of intermittent elevation in which were deposited beds which in some cases, as in Scotland, Sweden, and Eastern Canada, hold sea-shells, and in others, as in the central areas of North America, contain remains of plants of northern species. We shall name, for convenience, the parts of this Pleistocene revolution which include the great subsidence and glaciation, the _Glacial_ Age, that extending from the re-elevation to the modern the _Post-glacial_. The Glacial Age proved fatal to a large proportion of the land life of the previous periods. According to Professor Boyd Dawkins, out of fifty-three species known in Britain in the Post-glacial, only twelve are survivors of the Pliocene; and probably the proportions would not be greater in any part of the northern hemisphere. Some, however, did survive, either by migrating southward or by being inhabitants of places less severely affected than most by the general cold and submergence. There was thus no absolute break in the chain of life effected by the Glacial Age. TABLE OF PLEISTOCENE DEPOSITS IN SCANDINAVIA, ENGLAND, AND AMERICA. (Order descending.)