276 Bovie: NoNn-AVAILABLE WATER IN SOILS 
it becomes so concentrated that plants are unable to absorb more 
He went so far as to formulate a law, that the percentage of non- 
available water in soils increases as the square root of the percens 
tage of soluble salts. 
Before using, all soils were sifted with a screen possessing a 
quarter-inch mesh. Other than this, the physical condition of the 
soil was not given closer attention than to list it as ‘loose, medium, 
or hard in density.’ A plant was considered, by him, wilted, 
when its youngest leaves wilt strongly. This would seem to be a 
very unreliable criterion, for many plants, at least. A geranium, 
for instance, will not only maintain its younger leaves, but will 
put out new shoots, after its roots have been killed. Many other 
plants behave in a similar manner. 
Besides the above, a number of determinations of the amount 
of non-available water have been compiled, but aside from their 
local and immediate interest, they add nothing to our knowledge 
of non-available water.” 17 19 
ADSORPTION BY SOILS 
The work done previous to 1908, on adsorption, has been re- 
cently reviewed by Patten and Waggaman," so that a review of 
the literature need not here be given. The salient facts of interest 
in this connection are: Certain solids and liquids draw unto them- 
selves and retain within their structures, or on their surfaces, 
other solids, liquids, or gases.* This is called absorption. 
A special case of absorption, termed adsorption, is defined as the 
existence of a difference in concentration or density of a film 
adjacent to a bounding solid and the concentration or density of 
the mass of the liquid or gas which bathes the solid. t 
Whether the relation between the adsorbing and adsorbed sub- 
stances is physical or chemical, is not always clear; sometimes 
it appears to be one, sometimes the other. The difficulties in- 
volved in quantitative determination leaves us without a unit of 
adsorbing power, and with very few formule Erese the rate 
or conditions of adsorption. 
When an adsorbent is brought into contact with a solution 
containing two or more solutes, these solutes may be adsorbed in 
* Loe. cit. 10. 
1 Loc. Cit. 11. 
