The desultory, intermittent, extens

The desultory, intermittent, extensive use of the land practised by hunters and nomads tends, under the growing pressure of population, to pass into the systematic, continuous,intensive use practised by the farmer, except where naturepresents positive checks to the transition. The most obviouscheck consists in adverse conditions of climate and soil. Whereagriculture meets insurmountable obstacles, like the intensecold of Arctic Siberia and Lapland, or the alkaline soils ofNevada and the Caspian Depression, or the inadequate nun-fall of Mongolia and Central Arabia^ the land can produce dohigher economic and social groups than pastoral horde.Hence shepherd folk are found in their purest types in desertsand steppes, where conditions early crystallized the socialform and checked development, [Rainfall map chap. XIV.]