iqiq] ALWAY, McDOLE, b- TRUMBULL—SUBSOIL 189 



Experimental methods 



In taking the samples we used augers provided with extensions, 

 commonly employing two sizes, one i . 5 inches in diameter with 

 which to take the sample, and another 2.0 inches in diameter to 

 enlarge and clean out the hole preparatory to sampling the next 

 lower section. In many of the borings in western Nebraska the 

 subsoil in part or in all the levels sampled was too dry to be remov- 

 able by the ordinary auger, sliding off the bit as this was being 

 withdrawn. In such cases we employed a Tinsley "auger with 

 casing" (11), the sleeve on this retaining the soil loosened by the 

 bit. Except where otherwise indicated, the samples were com- 

 posites from 3 borings 10-20 yards apart. Composites were made 

 from the first 3 borings only where it could be seen from the behavior 

 of the soil toward the auger that the general moisture conditions in 

 all 3 were similar, but not necessarily identical. 



Extremes under semi-arid conditions 



After a prolonged drought.— As already stated, 1910 proved 

 the driest year in southwestern Nebraska since observations were 

 begun, the precipitation amounting to scarcely half the normal 

 (table III) . The autumn of this year and the following winter and 

 spring were practically without snow or rain until April, the total 

 precipitation at McCook from the end of August 19 10 to the first 

 of the following April amounting to only i . 60 inches (table IV), and 

 this fell in such small amounts as to influence the soil moisture 

 content through only a negligible distance. At Imperial and 

 Wauneta the weather was not quite so dry, but the difference was 

 not sufficient to cause an appreciable difference in the moisture 

 content of the subsoil. 



The samplings made in fields near McCook and Wauneta near 

 the end of October 19 10 showed such low ratios of moisture content 

 to hygroscopic coefficient (table V) that some undiscovered source 

 of error was suspected, and for this reason 6 weeks later we 

 resampled two of them, A and B at McCook, and took sets from 

 two additional fields. These confirmed the correctness of the 

 extremely low ratios. The concordance of the moisture content 

 with the hygroscopic coefficient was very striking, as though the 



