THE WATER OF SOILS. 217 



Sandy soils, especially when coarse, may absorb instantly even 

 a very heavy rainfall. Heavy clay soils when dry will at first 

 also absorb quickly quite a heavy precipitation; but as the 

 beating- of the raindrops compacts the surface, the absorption 

 quickly slows down, so that heavy downpours of brief dura- 

 tion, while wetting thoroughly into a plastic mass the first two 

 or three inches of a clay soil, may leave all beneath dry, to be 

 very gradually moistened by the slow downward percolation 

 against the resistance of the air in the soil; while the greater 

 part of the later portion of the shower will drain off the surface 

 in muddy runlets. Certain soils classed as loams, having the 

 property of crusting readily by rain followed by sunshine (see 

 chapter / , p. 1 1 1 ) , in heavy showers behave hardly better than 

 strong clay soils; shedding the water until the soaked crust 

 gives way, and is carried off in muddy streamlets. Then be- 

 gins the cutting-away of the soil that, in portions of the Cotton 

 States, as well as north of the Ohio river, has been the cause 

 of extensive devastation of once fruitful culture lands, the site 

 of which is now marked by " red washes " and gullies but too 

 familiar to the eye in many regions, especially of the southern 

 United States. 



Washing-away and Gullying in the Cotton States. Nowhere perhaps 

 have these effects been so severely felt as in portions of northwestern 

 and central Mississippi, and this case is so instructive as to deserve a 

 more detailed description. In the regions in question the soil stratum 

 consists of a yellow or brownish loam from three to seven feet in 

 original thickness, constituting a very desirable class of gently rolling 

 uplands, which at one time claimed to be the best cotton-growing 

 portion of the State. It was originally covered with an open forest of 

 oaks, with an abundant growth of grasses that afforded excellent pasture 

 to deer and cattle ; a natural park gay with flowers during most of the 

 season. 



When these lands were taken into cultivation little or no attention 

 was paid to the direction of the furrows and rows of corn and cotton ; 



that later, after the soil had been partially saturated, 6q/ only was absorbed in 

 the forested land, against 5% in the non-forested. While it is generally admitted 

 that forests diminish the runoff, Rafter (Relation of Rainfall to Runoff, U. S. 

 Geol. Survey Paper, No. 80, p. 53) contends that in New York State the reverse is 

 true. 



