Even during epochs of glacial advance conditions in France and in the German zone must have been better than we should expect. Some kind of grazing or browsing pasturage must have been rich and abundant to support large animals like the reindeer or even the woolly mammoths characteristic of the second and third glacial epochs, which furnished abundant food for prehistoric hunters. Farther south the glacial epochs may well have been times of heavy rainfall, transforming the Sahara desert and the dryer steppes and plateaus of Asia into veritable gardens. The retreating ice left behind it a land covered with rocks, clays, gravels, and sands brought by the glaciers and their streams. Here and there basins had been gouged out where lakes or ponds long remained--as in Maine and Minnesota to-day--to be later drained, or, if shallow, to be overgrown with sphagnum and changed into great bogs. Scattered thickets of shrubs and stunted hardy trees, poplars, willows, and others occurred. In sheltered and well-drained valleys and mountainsides the trees grew larger and even forests began to appear. This tundra landscape still characterizes wide areas of northern Canada and Siberia.[19] The tundra was followed by steppe conditions, where elevation of land to the north and northwest had cut off the tempering oceanic winds. The climate was harsh, dry, continental, with cold winters and hot summers. The winds carried great storms of dust and piled it up in drifts in valleys and on suitably situated mountainsides in the form of loess, so important to the future agricultural development of Europe, though its most massive accumulation is seen in China, which received and held the driftings from the great elevated plains of central Asia. As the climate became moister, if the temperature did not fall too low, steppe finally gave way to the meadow and forest of modern Europe. Tundra, steppe, and forest had each its special types of animal as well as plant life. The characteristic tundra animal is the reindeer, though musk-ox, woolly mammoth, and others were wide-spread at this time. The peculiar steppe animal is the horse. The characteristic forest and meadow animals are the deer and their allies; the wolf and bear; the wild boar and cattle seem to be at home in forest and glade and along the streams. In France, where there was far less glaciation, the succession of tundra, steppe, and forest is less apparent. Here we find a mingling of varied forms which have come in from very different regions, driven from their original homes by change of climate or drawn by favorable conditions.