44 BOARD OF AGRICULTURE. 



the scorching suns of summer, and it should not retain more 

 than nine-hundredths at any growing season. To maintain 

 this proportion of moisture, it is of the utmost consequence to 

 have a general and even distribution over the spring and sum- 

 mer months. 



It has been found, by accurate experiment, that the depth to 

 which rain water penetrates in a clayey soil (composed of 43 

 parts of carbonate of lime, 33 parts alumina, and 20 parts 

 sand) equals six times the depth of water fallen. A rain of 

 .04 of an inch would penetrate .24 of an inch of soil ; a rain of 

 .5 inch would penetrate 3.0 inches of soil; and so on. This 

 supposes the surface nearly dry when the rain falls. But sup- 

 pose a rain to fall before the preceding rain has wholly evapo- 

 rated, that is, before the earth is dry ; the rain penetrates still 

 deeper than before, increasing the depth of moisture. And 

 these lower strata, when once saturated, retain their moisture 

 of course longer than the surface, holding in reserve a fund of 

 moisture for the roots of plants in times of drought. 



During the winter months, or when the amount of evapora- 

 tion is not equal to the quantity of rain, all soils which retain 

 more than forty per cent, of water are wet. But when the 

 amount of evaporation exceeds or doubles the quantity of rain, 

 they dry up, and a drought succeeds. It is necessary, there- 

 fore, in order to know the severity of a drought, to study the 

 distribution of rain over the seasons, and the amount of evapo- 

 ration in the same seasons. The most serious droughts are 

 usually those that come in early spring, and after them those 

 that occur later in summer, during the ripening of grains. 

 Dry springs injure the grass and grain crops ; while an over- 

 abundance of rain sometimes causes the grain to blast, and the 

 Indian corn to turn yellow. Moist climates, like that of Eng- 

 land, are best for the grasses and root crops ; and those in 

 which such severe droughts occur, as in our own, require a 

 very different system of husbandry. 



It is evident, also, that the inclination of the soil must exer- 

 cise a marked influence over the quantity of water which it 

 would require to prevent its being two moist or too dry. 

 Sands require more moisture than clays. This is so well under- 

 stood in countries where irrigation is practised, that it is known 



