THE WATER OF SOILS. 



203 



months, reaches a maximum height beyond which the liquid 

 water will not rise. The ascent is most rapid, and stops 

 soonest, in coarse sandy soils; it rises most slowly, but 

 in the end considerably higher, in heavy clay soils. 

 The most rapid continuous rise, and ultimately the highest, 

 occurs in salty soils containing but a small propor- 

 tion of clay. The maximum height of capillary rise 

 thus far observed, viz. 10.17 feet, was noted in the case of 

 quartz tailings from a stamp mill, ranging from .005 mm. to 

 .016 mm. in diameter; but it took about 18 months' time to 

 reach this maximum. The excessively fine texture of clay 

 opposes great frictional resistance to the movement of the 

 water, and the same is true of the finest silts, which, like clay, 

 remain almost indefinitely suspended in water. But it must be 

 remembered that while pure grains of silt will in wetting re- 

 main unchanged in size, clay particles, and the clay incrusting 

 silt grains, will on wetting swell greatly, and thus fill up the 

 interstices, largely closing them up against the passage of 

 water. 



These facts are exemplified and graphically illustrated below. 



The soils selected for this illustration, from California lo- 

 calities, are the following: 



No. 233. Very sandy soil from near Morano, Stanislaus 

 County. Typical of the noted wheat-growing region of the 

 lower San Joaquin Valley, from northern Merced to Southern 

 San Joaquin Counties; bench or plains lands. First foot. 



No. 1197. Sandy alluvial soil from near the confluence of 

 the Gila and Colorado rivers, near Yuma. Very deep, light 

 and easily cultivated. First foot, but almost identical to 15 

 feet. 



No. 168. Silty alluvial soil from the old alluvium of the 

 Santa Clara River, near Santa Paula, Ventura County. Very 

 deep, very easily tilled; a typical alluvial loam of the arid 

 region. 



No. 1697. Black adobe or clay soil, from the experiment 

 station grounds, Berkeley. A heavy clay soil, originally a 

 swamp deposit, becoming very tenacious when wet. An ex- 

 cellent wheat soil. 



The physical analyses of these soils are given below. 



