THE SOIL SURVEY 727 



able to distinguish between the properties of the soil that 

 are native and permanent and those that may be induced 

 by the method of handling. There is very little knowl- 

 edge of natural phenomena that will not be found useful 

 to the field man in classifying soils, because he uses all 

 sorts of observations in making and checking his divisions 

 in soils. In brief, he should have a good training in the 

 fundamental technic of geology, chemistry, and agricul- 

 ture. 



In the way of physical equipment the field man should 

 have a good map of the region, on a scale of one inch to 

 a -mile or larger. The field work should be done on at 

 least as large a scale as the finished map, as this increases 

 the degree of accuracy. The map should show the roads, 

 streams, and towns of the region, and in addition the 

 topography, location of houses, and other natural and 

 cultural features which are useful in placing boundaries 

 of soil. Where a satisfactory map is not available the 

 field man must make such a map 1 during the progress of 

 the soil survey. For this purpose a Gannett plane table, 

 a sight alidade, and some method of measuring distance 

 preferably an odometer, such as is used for counting the 

 revolutions of a buggy wheel are necessary. Cloth- 

 back drawing paper is generally used. 



Where a suitable base map is already available, a set 

 of pencils of different colors for representing each type of 

 soil on the map as it is recognized is essential. A horse 

 and buggy is the usual method of conveyance. For ex- 

 amining the soil a soil auger is used (see Fig. 83). This 

 consists of a one-and-one-half-inch wood auger attached to 

 a half-inch pipe rod with a T handle, making a total length 



1 Instruction to Field Parties. U. S. D. A., Bur. Soils. 1914. 



