248 University of California Publications in Agricultural Sciences [Vol. 1 



have a peculiar light pinkish tint and are made up of alternating 

 strata of silt and a very plastic and impervious clay of varying 

 thicknesses. When this clay forms the surface soil, the difficulties 

 of cultivation and irrigation are very great ; but if the clay lies 

 at a depth of several feet below the surface of a silty soil then 

 the reverse i.s true. This peculiar type of land is represented in 

 the series by two columns of soil, one from the vicinity of 

 Imperial and the other from near El Centro ; these and that from 

 Coachella were taken by Mr. F. E. Johnson. 



Mojave River Mesa. — The mesa or plain is formed by accumu- 

 lation of granitic debris from the Sierra Madre Mountains on 

 the south and reaches far out toward Barstow, San Bernardino 

 County. This debris is coarse and quite compact, and in the 

 neighborhood of Victorville is said to have a thickness of thirty- 

 five feet or more. It is here overlaid by about three feet of a 

 gray sandy soil, also quite compact and supporting a sparse 

 vegetation of weeds. A column of eleven feet was obtained three 

 miles west of Victorville. The soil was found to contain but 

 0.13 per cent of humus in the surface foot, 0.14 per cent in the 

 second, 0.10 per cent in the third, and 0.08 per cent in the coarse 

 sand of the fourth foot. There were but traces of nitrogen in 

 the humus. The soil has 11.05 per cent of clay. 



Coachella Valleii. — A column was obtained from the vicinity 

 of Coachella and represents the higher and more sandy lands 

 that bordered the old Salton Lake of the Imperial country. 



Owens River Valley. — The agricultural lands of this valley 

 lie chiefly on the west side of Owens River and are formed of 

 the debris of the adjoining Sierra Nevada. A column of soil was 

 secured through the kindness of ]Mr. W. K. Winterhalter of San 

 Francisco. 



It was to be anticipated that the soils of what are known as 

 the desert plains of the eastern and southeastern part of the 

 state would be very poor in humus because of their very sandy 

 nature, together with small rainfall, extreme summer heat and 

 scant vegetation, but it was a surprise to find that humus occurred 

 at depths of twelve or more feet below the surface. The soil 

 poorest in humus is that from the mesa plain just west of 

 Victorville, in which plant roots were found in a depth of three 

 feet only, the underlying material being too compact for root 



