[Footnote 16: Much of this chapter is taken from The Solar Hypothesis of Climatic Changes; Bull. Geol. Soc. Am., Vol. 25, 1914.] [Footnote 17: Ellsworth Huntington: Explorations in Turkestan, 1905; The Pulse of Asia, 1907; Palestine and Its Transformation, 1911; The Climatic Factor, 1915; World Power and Evolution, 1919.] [Footnote 18: J. Hann: Klimatologie, Vol. 1, 1908, p. 352.] [Footnote 19: H. C. Butler: Desert Syria, the Land of a Lost Civilization; Geographical Review, Feb., 1920, pp. 77-108.] [Footnote 20: This is due to the fact that where these forests occur, in Gilead for example, the mountains to the west break down, so that the west winds with water from the Mediterranean are able to reach the inner range without having lost all their water. It is one of the misfortunes of Syria that its mountains generally rise so close to the sea that they shut off rainfall from the interior and cause the rain to fall on slopes too steep for easy cultivation.] [Footnote 21: H. Leiter: Die Frage der Klimaanderung waherend geschichtlicher Zeit in Nordafrika. Abhandl. K. K. Geographischen Gesellschaft, Wien, 1909, p. 143.] [Footnote 22: A most careful and convincing study of this problem is embodied in an article by J. W. Smith: The Effects of Weather upon the Yield of Corn; Monthly Weather Review, Vol. 42, 1914, pp. 78-92. On the basis of the yield of corn in Ohio for 60 years and in other states for shorter periods, he shows that the rainfall of July has almost as much influence on the crop as has the rainfall of all other months combined. See his Agricultural Meteorology, New York, 1920.] [Footnote 23: See chapter by A. E. Douglass in The Climatic Factor; and his book on Climatic Cycles and Tree-Growth; Carnegie Inst., 1919. Also article by M. N. Stewart: The Relation of Precipitation to Tree Growth, in the Monthly Weather Review, Vol. 41, 1913.] [Footnote 24: The dotted line is taken from Palestine and Its Transformation, pp. 327 and 403.] [Footnote 25: M. A. Stein: Ruins of Desert Cathay, London, 1912.] [Footnote 26: In the preparation and interpretation of this table the help of Mr. G. B. Cressey is gratefully acknowledged.] [Footnote 27: For the tree data used in these comparisons, see The Climatic Factor P. 328, and A. E. Douglass: Climatic Cycles and Tree Growth, p. 123.] [Footnote A: One year interpolated.] [Footnote 28: J. W. Gregory: Is the Earth Drying Up? Geog. Jour., Vol. 43, 1914, pp. 148-172 and 293-318.] [Footnote 29: Geog. Jour., Vol. 43, pp. 159-161.] [Footnote 30: See A. J. Henry: Secular Variation of Precipitation in the United States; Bull. Am. Geog. Soc., Vol. 46, 1914, pp. 192-201.] CHAPTER VI THE CLIMATIC STRESS OF THE FOURTEENTH CENTURY