Mfipping Soils and Alkali 



27 



cent of salt in the dry soil. The maps are to be constructed in the 

 field directly from the resistances. 



Standardizations have been made in 15 areas, and a study of the 

 curves reveals the fact that there is very little difference between 

 them; certainly no more difference between curves from different 

 areas than has been found by duplication of the standardization in 

 one area. The following table shows the standardization made 

 up from an average of these 15 curves. This table should be used 

 in all reconnoissance work and can be used in all alkali surveys, 

 except where it is found the curve does not give reliable results, 

 or where unusual accuracy is required. In such cases a new curve 

 should be made according to the instructions given. 



Average standardization — Table of limiting values. 



The difference between the resistances for the various grades of 

 soil is so small as to be within the limit of accuracy of the method, 

 so that hereafter texture may be entirely disregarded and the 

 figures in the last column used as the limiting values. 



For convenience, where it is desired to determine the percent- 

 age of alkali from the resistance at 60° F., the table on the follow- 

 ing page has been picked out from the average standardizations. 



