THE SOIL SURVEY 729 



moisture conditions of the sample are to be preserved, 

 wide-mouth, sealed-top, metal or glass containers should 

 be used. Aluminum cans are usually most suitable, as 

 they are not corroded by the sample. 



627. Procedure in the field. — The area for survey 

 having been selected, the field party — which usually 

 consists of two men, a chief and an assistant — proceeds 

 to examine the soils of the district. Headquarters are 

 temporarily established in a convenient village or coun- 

 try residence, and excursions are made into the adjacent 

 territory. The routes are laid out carefully and system- 

 atically with the purpose of examining the soils of the 

 entire area. The party proceeds along the highway, 

 with frequent stops and side excursions into the field, 

 examining the soil to a depth of three or more feet with 

 the auger. In humid regions the basis of the soil classi- 

 fication is a section of soil three feet deep. In arid 

 regions, where alkali is prevalent, a six-foot section is usu- 

 ally the basis of classification, and occasionally much 

 deeper examinations are made for studying the position of 

 the water table. The soil is examined especially with refer- 

 ence to its texture, structure, color, drainage, content of 

 organic matter, depth of different strata, and special chemi- 

 cal properties such as lime and alkali. The natural vege- 

 tation is observed, and note is taken of the type and 

 growth of crops as well as the extent and species of forest 

 trees. 



Borings and other observations are made from point 

 to point as the appearance of the soil, the topography, 

 the conformation of the country, and the character of the 

 vegetation may suggest. The frequency and position of 

 observations are determined entirely by the judgment of 

 the field man. They may be made every few rods or at 



