I 



SOILS. 39 



for the most part adobe-like. On the high phiteau the soils are 

 largelv colluvial. In the desert we encounter vast areas of liuht, 

 sandy soils, l)ut there are also extensive tracts of marls, clays, and 

 alluvial soils. 



Very few samples of soil were collected, as no general investigation 

 of the various types was attempted by the writers. It was observed, 

 however, that in Algeria there appear to l)e no important soils which 

 are not represented in California and Arizona by very similar types. 

 Obseivations were largely directed toward the comparison of Algerian 

 soils and their productivity with corresponding soils in America under 

 similar climatic ccHiditions. 



COAST REGION. 

 LITTORAL ZONE. 



An important and characteristic soil of the littoral zone is a bright- 

 red "adobe,"''' very conmion in the vicinity of Algiers, near Oran, and 

 elsewhere along the coast. It is sticky when wet and forms very hard 

 clods when dry, cracking to a depth of from 12 to 24 inches. This 

 soil is often naturally poor in phosphoric acid, nitrogen, and lime, l)ut 

 responds readily to treatment. Its potash content is generally ade- 

 quate. It is an excellent soil for vineyards, except in cases where a 

 lime "hardpan" occurs too near the surface. Some of the best wines 

 of Algeria ai'e produced on soil of this t^^pe. The American soils 

 which most nearl}' resemble it are the San Joaquin red adobe, as it 

 occurs in the San Joaquin and Sacramento valleys, and the Fullerton 

 sandy adobe of the coast region of southern California. 



A mechanical anah'sis of one specimen of this soil is given on page 

 40, under No. 7663. This sample was collected a few miles south of 

 Oran, and represents the heaviest phase of this red soil. We have 

 not found in America a type of red adobe in which the average clay 

 content is so high. The black adobes of the United States are some- 

 times verv claye}', but most American adobes contain more silt than 

 clay. The same soil type was also observed at Arzeu, in western 

 Algeria, at various localities near Algiers, and, to a less extent, around 

 Tizi Ouzou, in Great Kabjdia. 



River bottoms in the littoral zone are characterized l\v soils that are 

 (luite diflerent from the red, clayey type just described; and are, in 

 fact, mere continuations of the soils of the next zone. They are 

 usually alluvial deposits, clayey or marly in texture, and are quite 

 feitile. They contain an al)undance of potash, though they are some- 

 times deficient in phosphoric acid. 



VALLEY AND PLAIN ZONE. 



The large vallevs, which in .some ca.ses are so extensive as to be 

 virtually plains, contain a great variet}' of soils. The plains of the 



