1889.] PUBLIC DOCUMENT — No. 4. 41 



from the soil, either directly or indirectly, are compara- 

 tively uniform, they are usually estimated in considering 

 the water supply of cities at from nine to sixteen inches of 

 rainfall ; in this country, with its drier and warmer climate, 

 they are very variable, but are found on the average to equal 

 about one-half of the rainfall ; or say from fifteen to thirty 

 inches of water.* The authority quoted, continues: "As 

 illustrating the difierence in capacity to absorb moisture of 

 the atmosphere of the two countries (England and America) , 

 it may be stated, that the mean yearly evaporation from 

 water surfaces was determined by six years of experiment at 

 Whitehaven, England, to be 30.03 inches ; while experi- 

 ments lasting for one year at Ogdensburg, N.Y., showed 

 it to be there 49.37 inches, and at Syracuse, N.Y., 50.2 

 inches. Observations taken at Salem and Cambridge, Mass. , 

 determine it at about 56 inches." In experiments with 

 water surfaces at Plaistow,f England, the rate of evapo- 

 ration was found to be 91.2 per cent of the rainfall, and 

 trials at Dijon, in France, gave the rate as 96.6 per cent of 

 the rainfall. At Orouo, Me., J evaporation from a water 

 surface during the period from May 20 to October 17, was 

 18.54 inches; and at Milwaukee, Wis., from March 15 to 

 November 14, as a five years' average, 32.58 inches. 



From a soil surface, we have it stated by Dr. Dalton § as 

 the result of observations during the years 1796 and 1798, 

 in England, that the mean evaporation was 25.158 inches, 

 and for the six months, April to September, inclusive, 16.788 

 inches, the largest amount being 4.095 inches in July, and 

 3.386 inches in August. Later, Mr. Dickinson || determined 

 the average evaporation from a lysimeter for equal years, 

 1836 to 1843, as 15.320 inches, or 57.6 per cent of the rain- 

 fall. Other foreign determinations H are those at Rotham- 

 stead, the average of five years, 63.2 to 71.4 per cent of a 

 28-inch rainfall ; those at Geneva, Switzerland, 61 per cent 

 of a 26-inch rainfall ; those at Orange, France, 80 per cent 



* Report of the Cochituate Water Board for 1873, p. 11. 

 t Jour, of Agr. 2d ser., xii., p. 400. 



I Femald. Agr. of Me., 1869-75. 



§ Mem. of the Lit. and Phil. Soc. of Manchester, v. pt. 11. 



II Jour. R. A. S. 1856, p. 127. 



H Scientific Farmer, Feb. 1878, p. 17 ; Feb. 1879, p. 15. 



