Relation of Xonauailable Water to Hygroscopic Coefficient 79 
perature conditions but to great differences in precipitation, if 
we assume that since the close of the glacial epoch there has been 
but little change in the climate of what is now Nebraska. In the 
extreme eastern part the normal precipitation is over 30 inches, 
while in the southwestern corner it is less than 20, there being a 
gradual decrease from east to west as shown on the accompany- 
ing map. While the precipitation decreases from east to west, 
there is a rapid rise in the rate of evaporation. As the precipita- 
tion falls chiefly during the growing season there is but little 
ii i 
Pig. 19. Roots of Mexican 
beans; experiment of 1910. 
seepage from the level prairies in the eastern portion and practi- 
cally none from those in the western. Uniformity in phvsical 
properties has long been recognized as characteristic of the Ne- 
braska loess and a recent chemical study 1 has shown that, except 
in the content of calcium carbonate, which increases from east to 
west, the chemical composition is very uniform. 
Field studies of soil moisture had indicated that there was a 
1 Alway, F. J. Composition of the Loess Soils of the Transition Region. 
Eighth International Congress of Applied Chemistrv, 1912, Report of 
Section VII. p. 11. 
