ALKALI CONDITIONS IN THE &ALTON BASIN.-' 101 



It should be noted that the alkali occurring NUM-IHY parts 'df the Salt 

 River Valley, represented by this sample, is of a different type from 

 that found in the Algerian Sahara and in the Salton Basin, California. 

 In the last-named regions the alkali is of the "white" kind and con- 

 tains only very small percentages of carbonates or bicarbonates. In 

 the Salt River Valley sample, on the contrary, the alkali is of the 

 so-called "black" sort, and contains an appreciable amount of the 

 highly poisonous sodium carbonate, which is much more injurious to 

 most plants than is "white alkali." Black alkali is intensely alkaline 

 in reaction, a and because of this reaction is highly corrosive to the 

 roots of plants. It also has the property of dissolving the humus of 

 the soil, which causes the formation of black crusts and of black spots 

 in the fields where this type of alkali is abundant; whence the name. 



From the thrifty growth of the date palms in the Cooperative Date 

 Garden at Tempe, Ariz., in soils approximating the above sample in 

 the amount and nature of their alkali content, it is probable that the 

 date palm is able to resist small quantities of black alkali. Further 

 researches are, however, needful to settle this point. (See p. 120.) 



ALKALI CONDITIONS IN RELATION TO DATE CULTURE IN THE SALTON 



BASIN, CALIFORNIA. 



GEOGRAPHY AND GEOLOGY OF THE SALTON BASIN. 



The Salton Basin, or Colorado Desert, (see PL IV, p. 122, fig. 10, 

 p. 102, and PL XVIII, fig. I), 6 is a basin the center of which is far 

 below sea level (some 263 feet below at Salton). It is surrounded by 

 mountains on three sides, and is limited on the south by sedimentary 

 deposits of the delta of the Colorado River which have piled up con- 

 siderably above the sea level. The high San Jacinto Mountains on 

 the west effectually protect the basin from the cold and humid winds 

 from the Pacific Ocean, while the still higher San Bernardino Moun : 

 tains form a barrier on the north that stops the cold winds that sweep 

 across the Mohave Desert; on the east, San Bernardino and the lower 

 Chocolate Mountains limit the basin. 



That part of the Salton Basin which lies below sea level was covered 

 until comparatively recent times by the Gulf of California, which then 

 extended much farther north than now. The Colorado River, which 

 then flowed into the gulf near where Yuma is now situated, brought 

 down at flood times an enormous mass of sediment, which gradually 



Alkali, in spite of its name, is often composed of neutral salts, such as sulphates 

 and chlorids, and has in consequence no pronounced alkaline reaction. (See p. 72.) 



& See also Pis. LXXXVII. to XCV, Means and Holmes, Soil Survey around Impe- 

 rial, Cal., in Field Operations of the Bureau of Soils, Third Report, 1901; also 

 Pis. XXIII to XXVI, Coville and MacDougal, Desert Laboratory of the Carnegie 

 Institution, Publication No. 6, Carnegie Institution of Washington, November, 1903. 



