468 University of California Publications in Agricultural Sciences [Vol.3 



On the basis of the preceding results and discussions some general 

 treatment is possible, as well as a more or less critical discussion of the 

 methods of soil surveying pursued by the Bureau of Soils. 



The types and the localities of collection of the soils studied were 

 as follows : 



Diablo clay adobe: Thalheim (17) 



San Juan Capistrano (1) Madera (18) 



Los Angeles (2) Merced (21) 



Calabasas (5) Del Mar (26) 

 Danville (6) Hanford fine sandy loam: 



Alt a mo nt clay loam Elk Grove (14) 



Walnut (3) Aeampo (15) 



San Fernando Valley (4) Woodbridge (16) 



Mission San Jose (7) Waterford (19) 



San Joaquin sandy loam: Snelling (20) 



North Sacramento (10) Basset (22) 



Lincoln (11) Anaheim (23) 



Wheatland (12) Los Angeles (24) 



Elk Grove (13) Van Nuys (25) 



Note. — Figures following localities designate sample numbers. 



Comparisons of Physical Data 



The mechanical analyses of the soils were carried out with both 

 the Hilgard elutriator and the Bureau of Soils centrifuge methods. 

 The tedious nature of the elutriator method has been emphasized else- 

 where. The results by this method show that the soils of each type 

 as a whole are somewhat similar, though no two are identical and 

 some samples of a type are widely divergent from the rest. The 

 Bureau of Soils method appears to give a sharper and more satisfac- 

 tory separation into classes than does the elutriator method. This is 

 to be expected since the separates represent greater ranges of particle 

 sizes. As a check on the texture of the samples collected, it shows that 

 some of the soils are not true to name, therefore that all soils mapped 

 under a given type name are not closely similar to one another. Of 

 course, this is the belief of many soil surveyors, but it seems strange 

 that in the present work, where there was the attempt to select soils 

 representative of the class and type chosen for study, that such diver- 

 gences developed. It is an interesting commentary on the personal 

 equation of the field worker, in this case of the writer, who collected 

 the samples. 



