74 EDITORIAL 



A Sketch of the Pedological Geology of California. By E. W. Hil- 

 gard, Berkeley, Cal. 



Owing to the great climatic diversity, the rainfall varying from two 

 inches at the south to as much as eighty inches in the north, even a 

 sketch of the soil conditions of California must take the climates into 

 consideration. The cardinal difference between rock decomposition 

 in arid as compared with humid climates lies in the retardation of kao- 

 linization, as exemplified in the monoliths of Egypt and the granites 

 of the Sierra Madre, as compared, e. g., with the Alleghanies. Hence 

 in northern California and on the higher Sierra Nevada we find loams 

 and clay soils, while at the lower levels and in southern California the 

 soils are "dusty" or sandy, except where derived from preexisting 

 clay formations, which give rise to " adobe," and in the upper valleys 

 of the rivers of the Sierra, which carry the materials from the higher 

 levels. 



Throughout the middle and southern parts of the state, where no 

 rains of consequence fall between May and November, not only is the 

 soil mass usually of extraordinary depth, but is scarcely changed for 

 several, sometimes for four to ten, feet. There is practically no subsoil 

 in the usual sense, in the absence of clay; water, roots, and air pene- 

 trate together to depths impossible in the regions of summer rains, 

 and hence the extraordinary endurance of drought, even by plants 

 foreign to the arid region. Moreover, these soils almost universally 

 contain high percentages of lime and potash, due to the absence of 

 the leaching process, which, on the other hand, results in the forma- 

 tion of " alkali soils," too complex a subject to be dealt with here. 



" Sand" in the arid soils is not merely quartz grains, but consists 

 of all the original minerals, superficially decomposed. Hence sandy 

 lands are here fully as rich as clay lands are elsewhere. 



In the Great Valley it is easy to recognize by their microscopic 

 characters the alluvial areas of the several rivers coming in from the 

 Sierra. Even here the greater rainfall of the Sacramento is evidenced 

 by loam and clay lands, as compared with the San Joaquin valley, 

 where sandy and silty lands prevail altogether. As the rainfall decreases 

 toward the Coast Ranges, the "lightest " are found under the arid lee 

 on the west border of the valley. In its axis, in the "tule lands," as 

 well as on the borders of the bays near its outlet, heavy clay soils are 

 being formed in the slack water, while the streams coming from the 

 Coast Ranges are bordered by light silty lands, the " truck lands " from 



