96 RELATIONS OF SOIL TO WATER 



assume practical importance. Capital illustrations of the 

 influence of various conditions on the height to which water 

 is raised, and the quantity lifted, are furnished by the experi- 

 ments of Johnson and Armsby with loam and emery 

 (Connecticut Exp. Stat. Rep. 1878, 83); the latter substance 

 was selected because it can be procured in commerce graded 

 in various degrees of fineness. 



A loam was separated by sifting into particles of three 

 grades. Tubes fourteen inches long and two inches in 

 diameter were filled with these soils ; the lower ends of these 

 tubes were then placed in water. The quantity of water 

 evaporated by each soil in 150 days per square inch of surface 

 was as follows : 



Average Diameter Wafer Evaporated 



of Soil Particles. per square inch. 



3-0 mm 49-2 grams 



1-0 73.8 



less than 0-25 153-8 



We see that as the size of the soil particles diminished 

 there was a large increase in the quantity of water brought 

 to the surface. In the case of the two coarser materials the 

 amount of water raised was insufficient to preserve a moist 

 condition at the surface ; the action in these cases was thus 

 mainly due to a mere surface distribution of water. 



The next experiment we quote shows the influence of 

 varying height on the quantity of water raised. The trials 

 were all made with emery of one kind, the average diameter 

 of the particles being 0-229 mm. The experiment lasted 

 twenty-five days. 



Relative Heights Water Evaporated, 

 of the Columns. 



1 133-9 grams 



2 118.2 



3 112-0 



