As the land began to rise, the first effect was an increased snowfall on the higher summits, and increased rainfall on the rising coast lands. The rivers had an increasing fall towards the sea, and rapidly carved out deep narrow valleys, which were later developed by the ice into the great fiords of Norway and other heavily glaciated regions. But on the whole the first beginnings of the Ice Age occurring towards the close of the Pliocene period are obscure, and are likely always to remain so, for the simple reason that the advancing and retreating ice-sheets have wiped out most of the evidence of the conditions which immediately preceded their advent. The deteriorations of the climate had begun long before the geographical changes outlined at the close of the last chapter were complete, for mollusca of the Pliocene beds in East Anglia indicate progressive refrigeration of the North Sea at the same time as it became increasingly shallow. At the close we have great shell-banks with northern species which must have been piled up by powerful easterly winds; these easterly winds show that the storm-tracks had been driven south of their present course and suggest that the glacial anticyclone already existed over Scandinavia. At the present day similar shell-banks are forming on the coast of Holland under the influence of the prevailing westerly winds. The next series of deposits in this region are fresh-water “forest beds,” attributed to a greatly extended Rhine, and belong to the period when the North Sea had become a plain. It is no part of the plan of this work to go over the geological ground of the Quaternary Ice Age, which has already been so frequently and so efficiently covered. All I can hope to do is to give a brief general account of the succession of climatic changes involved, necessarily incomplete since so much of the world is at present insufficiently explored for glacial traces. But a certain amount of explanatory introduction is necessary. In Europe and North America there are distinct traces of several separate glaciations with “interglacial” periods when the climate approached or became even warmer than the present. The time-relations of these glaciations are not yet fully worked out, but there seems little doubt that they were contemporaneous in the two continents. The correlation is not perfect, however, since the United States geologists recognized altogether five glaciations. The explanation appears to be that the equivalent of the Rissian glaciation in America is double; two stages, the Illinoian and Iowan, being recognizable, separated by a retreat of the ice. The series is as follows: