320 REPORT UNITED STATES GEOLOGICAL SURVEY. 



tnruips, peas, and the hardier garden vegetables, are safe crops at any 

 elevation under 7,500 feet. Potatoes and turnips generally do well up 

 to 9,000 feet. Wheat grows splendidly at as high an elevation as 9,000 

 feet, but above 7,500 feet it is a hazardous crop, liable to be iujured by 

 early frosts or snow. Oats grow well up to 9,000 feet, but generally do 

 not ripen at this elevation." 



Mr. E. L. Berthoud, C. E., of Golden City, Colo., writes me as fol- 

 lows on this subject : " Turnips grow and yield well up to 9,200 feet. 

 Potatoes grow, but yield only fairly up to 9,200 feet, and at 9,000 feet the 

 tops get frosted. Wheat does not ripen above 7,500 feet. Barley and 

 oats scarcely ripen, and only in exceptional seasons, above 8,200 feet. 

 Corn does not ripen above 5,700 feet. Wild grapes grow well up to 

 6,000 feet ; cultivated grapes up to 5,800 feet. Pear-trees do well up 

 to 5,750 feet. Buckwheat is so uncertain that it is not possible to give 

 certain data as to altitude, but some has been raised at 7,400 feet. 

 Except on the Arkansas Eiver, Eio Grande, and lower Fontaiue qui 

 Bouille, corn is no crop in Colorado east of the (continental) divide." 



These figures are liable to slight modifications from the influence of 

 latitude and local causes, but in general they are correct. 



AMOUNT OF WATER USED IN IRRIGATION. 



The quantity of water applied by irrigation to various crops ranges 

 within very wide limits in different parts of the earth. The require- 

 ments of the crops differ with the character of the season, whether wet- 

 or dry, and with the nature of the soil, whether clayey or sandy, &c. 



An " inch of water" to the acre is a very common allowance in the 

 State. An inch of water is the amount which will flow through an 

 aperture 1 square inch in section in the course of a season ; an amount 

 which, of course, varies with the pressure from head or velocity. 



In reference to this subject, Mr. E. S. Nettleton, of Pueblo, Colorado, 

 has written me as follows: "It is impossible to give any rule for the 

 quantity of water required to irrigate crops of different kinds. Land 

 that has been irrigated for several years requires less water than new 

 land. Clay lands require less than sandy lands. Yery level land takes 

 more water than sloping or rolling lands. * * * Crops which are 

 sown broadcast require more water than those sown in drills or planted 

 in rows. Early sown or planted crops, as a general thing, require less 

 water than those sown or planted late. It is considered economical to 

 irrigate in the latter part of the day or evening, especially in hot weather. 

 Corn requires less water than almost any other crop, especially the Mex- 

 ican variety. Oats and grass require the most. An iuch of water to 

 the acre is the rule of some. This may be half enough in some in- 

 stances, in others it may be double or even three times the quantity re- 

 quired." 



In regard to this question. Marsh, in his "Man and Nature," page 377, 

 et seq., says: "As near as can be ascertained, the amount of water ap- 

 plied to irrigated lands is scarcely anywhere less than the total iDrecipi- 

 tation during the season of vegetable growth, and in general it much 

 exceeds that quantity. In grass groands and in field-culture it ranges 

 from 27 or 28 to 60 inches, while in smaller crops, tilled by hand-labor, it is 

 sometimes carried as high as 300 inches," and adds, in a foot-note, quoting 

 from Niel, " Agriculture des Etats Sardes," " that the practice in Lom- 

 bardy is to give the equivalent of 32 inches of precipitation in 100 days, 

 that being the estimated length of the irrigatiug season |" and that in 

 Germany, quoting from Boussingault, "Economie Eurale," "Grass 



