204 



SOILS. 



PHYSICAL ANALYSES OF TYPICAL SOILS. 



The most striking feature in this diagram is the very rapid 1 

 and high ascent in the combination of sediments represented 

 by the Gila bottom soil. It outstrips at once both the sandy 

 soil from Stanislaus, which contains a trifle less of clay, and 

 the silt soil from Ventura, from which at first sight it does not 

 seem to differ widely, but which contains considerably more 

 clay. It is doubtless the latter which so greatly retards the 

 motion of the water, as is still farther seen in the case of the 

 clay or adobe soil. It will be noted that on the second and 

 third days, the Gila soil had raised the water nearly twice as 

 high as the adobe, and that it took only 18 hours to raise it 

 nearly the same height as that attained by the Ventura silt in 

 so many days. But it ceased to rise after the 1251!! day, 

 while the Ventura soil, continuing for 195 days, finally rose 

 3 inches higher. The adobe also continued its rise, but did not 

 reach the same height as the Gila soil by nearly two inches. 

 There can be no doubt that the energetic and high rise of the 

 latter proves an important factor in the culture of these lands. 



The coarse sandy soil reached its highest limit, i6 l / 2 inches, 

 within six days, when the silty Gila soil stood at about double 

 that height. 



Ascent of Water in uniform 2 Sediments. Loughridge has 

 ascertained the rate of ascent of uniform sediments of differ- 

 ent grain-diameters, with the results shown in the diagram 



1 The ascent is of course most rapid, in the large tubes almost instantaneous, 

 when the capillary space is entirely clear ; but in the complex system of con- 

 nected air spaces in soils, the curved paths and the friction obstruct the move- 

 ment. 



2 I. e., uniform between the narrow limits given. 



