1889.] PUBLIC DOCUMENT — No. 4. 43 



cultivated region, the figures for evaporation may be con- 

 sidered as approximately similar for the several localities. 



We may now review our scientific data, by stating the fol- 

 lowing propositions as approximately correct : — 



1. The amount of water contained in one corn crop is 70 

 times that of the nitrogen and ash constituent, and amounts 

 to about 79 per cent of the weight of the plant. 



2. The amount of water transpired from one corn crop 

 during its growth is equivalent, at the least, to from 2 to 3 

 inches of rainfall. 



3. The amount of water lost from the soil through evap- 

 oration during the growing months is over 98 per cent 

 of the rainfall at South Framingham, Mass., and over 84 

 per cent at Geneva, N. Y., as measured by the lysimeters ; 

 or allowing for surface drainage, which occurs on natural 

 areas, is probably at least 100 per cent of the rainfall or 

 more. For the year, from natural areas, this loss is over 50 

 per cent of the rainfall ; as measured by the lysimeter in 

 Massachusetts, about 82 per cent of the rainfall ; at Geneva, 

 N. Y., 73 percent. 



Passing now to practical data, which may wisely take the 

 form of propositions, as being verifiable by common experi- 

 ence, we may note as of importance for our purpose : — 



1. The variation of crop as between difierent years is far 

 greater than occurs the same year between different fields 

 diflferently fertilized, under conditions of fairly good farm- 

 mg, thus proving the importance to farming of the condi- 

 tions generally included under the concrete terms, season and 

 climate. 



2 . The variation in crop between difierent fields of similar 

 treatment is manifestly dependent on the soil relations to 

 moisture, as may be readily verified by careful and intelli- 

 gent observation and trial. 



3. The conditions of climate (or season) which principally 

 affect the crop, as recognized yearly by farmers, is the 

 greater or less amount of rainfall, as the farmer construes 

 his observations ; or, as the more observant man construes it, 

 the distribution of the rainfall, and the extent of evapora- 

 tion. (August, on the average, is the month of greatest 

 rainfall, and usually greatest drought.) 



