132 University Geological Survey of Kansas. 
this action would not take place, and on such soils gypsum 
would be of no value; if too much humus, the action would 
be rapid, setting free so much sulphuric acid that it would cor- 
rode the roots of plants and so prove injurious. The lime of 
plants shown in the table given was supposed by ahi to re- 
sult from the decomposition of gypsum. 
The sulphur of plants probably comes from other sulphates 
more easily decomposed than gypsum, though a portion may 
result from this mineral. Most of the lime is from other com- 
pounds, especially the carbonate of lime, which is readily soluble. 
RECENT THEORY OF STORER. 
Gypsum is now thought to act as a fertilizer of soils in three 
ways, one mechanical and two chemical. 
First, lime is known to flocculate loose soils; that is, collect 
together the loose particles and make the soil more granular. 
This may be illustrated by placing lime in a muddy liquid, and 
the mud will flocculate and settle to the bottom. Lime also has 
an opposite effect on tough clay soils, where it granulates them, 
breaking the soil up into finer portions. Gypsum, as a lime 
salt, appears to act to a small extent in these ways and so im- 
proves the mechanical condition of soils; but in this respect 
other lime compounds act more powerfully and moré rapidly, 
and so would be better. 
Second, Storer” has pointed out that gypsum has nearly one- 
half its weight in oxygen and gives this up to many substances, 
and so may act upon nitrogenous and carbonaceous substances 
in the soil. 
Third and most important, it has been shown that gypsum 
decomposes the double silicates in the earth, setting free potash 
as a soluble sulphate. According to Storer the action is as fol- 
lows : 
AleOs| | AleOs) 
Ko 1 XSiO:+CaOSO; = FAO }XSi02+4+1K2080s 
H2O J H20 J 
52. Chemistry of Agriculture, Vol. 1, pp. 206-216, 1887. 
