═════════════╤══════════════ │ KERN COUNTY. ─────────────┼───────┬────── │Summer.│ Kern │ │Island ─────────────┼───────┼────── │Alkali │Alkali │ crust │crust ─────────────┼───────┼────── Soluble salts│ │ in 100 │ │ parts soil │ │ Potassium │ │ 4.72 sulfate │ │ [E]Potassium │ │ nitrate │ │ Potassium │ │ carbonate │ │ (Saleratus)│ │ Sodium │ 19.20│ 70.61 sulfate │ │ (Glauber’s │ │ salt) │ │ Sodium │ │ 14.82 carbonate │ │ (Sal-soda) │ │ Sodium │ 37.14│ 4.13 chlorid │ │ (Common │ │ salt) │ │ [E]Sodium │ │ phosphate │ │ Calcium │ 0.96│ 0.08 sulfate │ │ (Gypsum) │ │ Magnesium │ 18.31│ sulfate │ │ (Epsom │ │ salt) │ │ Organic │ 20.87│ matter │ │ ─────────────┴───────┴────── Footnote F: Common and Glauber’s salts. =50. Adobe Soils.=—In many parts of the arid regions of this country which can be recovered for agricultural purposes by irrigation the soil has peculiar characteristics. The name adobe as commonly used applies to both the sundried bricks of the arid regions of the West and Southwest, and to the materials of which they are composed. The material is described by Russell[34] as a fine grained porous earth, varying in color through many shades of gray and yellow, which crumbles between the fingers, but separates most readily in a vertical direction. The coherency of the material is so great that vertical scarps will stand for many years without forming a noticeable talus slope. _Distribution._—The area over which adobe forms a large part of the surface has not been accurately mapped, but enough is known to indicate that it is essentially co-extensive with the more arid portions of this country. In a very general way it may be considered as being limited to the region in which the mean annual rain-fall is less than twenty inches. It forms the surface over large portions of Colorado, New Mexico, Western Texas, Arizona, Southern California, Nevada, Utah, Southern Oregon, Southern Idaho, and Wyoming. Adobe occurs also in Mexico and may there reach a greater development than in the United States, but observations concerning it south of the Rio Grande are wanting.