October 6, 1911] 



SCIENCE 



431 



each 40-acre lot with another living in town 

 or depending on transportation for livelihood; 

 when the aggregate population would reach 

 200,000,000, or twenty times that of to-day. 



Over the 800,000,000 acres of the westward 

 states the rainfall ranges from less than 2 to 

 over 100 and averages about 12 inches, aggre- 

 gating some 800,000,000 acre-feet yearly, or a 

 fifth of the productivity standard. The entire 

 water supply would sufBce for the intensive 

 cultivation of only 160,000,000 acres; but the 

 present and prospective utilization is highly 

 efficient (the " return water " from irrigation 

 is used over and over again), so that the pos- 

 sible population may be estimated at 200,000,- 

 000, or thirty times that of to-day. 



These estimated populations are comparable 

 with present populations in several countries. 

 The 600,000,000 for the eastward states is 

 about one fifth greater than that of China 

 (438,214,000) and Japan (50,751,919) com- 

 bined; the density is 500 per square mile, 

 almost exactly that of Lombardy (495), little 

 above that of the Netherlands (467), only li 

 times that of the United Kingdom (372), 

 little more than three fourths that of Belgium 

 (649), two thirds that of Saxony (778) and 

 half that of (settled) Egypt (931). The 200,- 

 000,000 for the median states is considerably 

 less than the population of British India 

 (231,855,583); the density is 333 per square 

 mile, below that of Japan (344) but above 

 that of Alsace-Lorraine (324), Germany (311) 

 and Italy (310), not greatly above that of 

 China (266), and little more than half that of 

 Java (595). The 200,000,000 for the westward 

 states would give a density of 167 per square 

 mile, the same as that of Denmark and Hun- 

 gary and considerably below that of France 

 (190), Switzerland (234), Bavaria (223), For- 

 mosa (226), Austria (246) or Poland (232).' 

 The aggregate of 1,000,000,000 for mainland 

 United States is comparable with the present 

 population of Asia or twice that of Europe; 



* The figures are taken (the population-deiisity 

 generally computed) from areas and populations 

 in the "Statesman's Yearbook," 1910, supple- 

 mented by records for 1910 compiled by Gannett 

 (Nat. Geog. Mag., Vol. XXII., 1911, p. 785). 



the mean density is 333 per square mile, about 

 mid-way between that of the United Kingdom 

 and Germany, little more than half that of 

 Belgium, less than half that of Saxony and 

 only about one third that of Egypt. 



The rate of increase in population to the 

 limit fixed by water supply may be extra- 

 polated roughly; and despite the favorable 

 prepossesion due to Gannett's experience 

 (greater perhaps than that of any other cen- 

 sus student in the country), his estimate of 

 the decennial increment may be somewhat in- 

 creased — for several reasons. In the first 

 place his estimate for the 1910 population, 

 although made but a few months in advance 

 of enumeration and in the light of the ap- 

 proximate figures of late prepared in the 

 Census Office, was nearly 2,000,000 too low. 

 Again, the advance during recent years in 

 etiology, sanitation, surgery and other factors 

 of health and viability have virtually given a 

 new lease of life to mankind in this and other 

 countries, while the influence of enlighten- 

 ment is rapidly spreading, so that (in spite of 

 a declining birth-rate) the population of the 

 world generally appears to be increasing at an 

 unprecedented rate. Furthermore, in this 

 country primary production {i. e., of food- 

 stuffs and textiles) has within a few years 

 past increased with unparalleled rapidity, per- 

 haps more rapidly than manufacturing or 

 transportation in their palmiest days; taking 

 the value of the farm products of 1899 at 100 

 as a basis, the relative value for 1905 was 133 ; 

 for 1906, 143.4; for 1907, 158.7; for 1908, 

 167.3; for 1909, 182.8, and for 1910, 189.2— 

 the absolute value for this last year reaching 

 $8,926,000,000.' Meantime the influx of pro- 

 lific immigrants continues, and a large pro- 

 portion of them are finding their way into 

 rural districts and primary industries where 

 the conditions are favorable to family life. 

 These various considerations warrant the ex- 

 pectation of a vigorous and sustained growth 

 in the population of this country for many 

 years. 



It is true that apparent indications of ap- 



= ' ' Yearbook of the Department of Agricul- 

 ture," 1910, p. 10. 



