The climate is healthy in the uplands, though subject to violent changes; in the valleys fever is very prevalent, especially in the basins of the Boyana, the lower Drin and the Simen.
The region of the Red River and Assiniboine valleys was opened up by the fur traders, who came by the waterways from Lake Superior, and afterwards by the water communication with Hudson Bay.
The greater part of Patagonia is comparatively barren and has no arboreal growth, except in the well-watered valleys of the Andean foothills.
The hilly regions of Limousin, Prigord and the Cvennes are the home of the chestnut, which in some places is still a staple food; walnuts grow on the lower levels of the central plateau and in lower Dauphin and Provence, figs and almonds in Provence, oranges and citrons on the Mediterranean coast, apricots in central France, the olive in Provcnce and the lower valleys of the Rhneand Durancc. Truffles arc found under Silk Cocoons.
The exact form of these three interior valleys, which had an important influence on the construction and history of the city, is still imperfectly known, as they are to a great extent obliterated by vast accumulations of rubbish, which has filled them up in some places to a depth of more than 100 ft.