6 
Colorado Experiment Station 
make out so strong a case against lime as it appears to, for trees do 
well and live to an old age in limestone countries; so this effect is 
either peculiar to gypsum or to the arsenic which is frequently present 
in it. 
There are difficulties introduced by retaining the calcic sulfate 
as a component of our alkalis, but I have consistently retained it, and 
that for the reasons indicated. It is seldom, however, outside of cases 
like the apple trees that questions of the possibly poisonous character 
of the calcic sulfate are raised. Sometimes shallowness of soil over a 
gypsiferous layer, or the impermeability of this layer may give rise 
to mechanical troubles which are entirely distinct from the effects al¬ 
luded to above, which may also be present at the same time. I recall 
a very bad case of an orchard in which this was the case and both diffi¬ 
culties had to be contended with. But I would in no way consider my¬ 
self justified in considering the case as an instance of alkali trouble. 
The question regarding magnesic sulfate is not wholly unlike that 
of the calcic sulfate but is somewhat turned around. Experiments 
have shown that magnesic sulfate is quite poisonous but its presence in 
alkali in the soil does not actually prove so detrimental as our ex¬ 
periments would lead us to expect it to be. I have only made sprout¬ 
ing experiments in sand to which this salt had been added in as large 
quantities ( 2.5 percent of the dry sand) as we are likely to meet with 
in any of our soils. The germination was delayed but not prevented 
and the little plants grew well for the few days that we observed them. 
I do not think that anyone has questioned the propriety of including 
magnesic sulfate among the alkalis. 
ORIGIN OF THE ALKALIS 
There is unanimity in regard to the origin of the alkalis; briefly 
stated it is explained as follows: The earthy mass that we term soil 
is, from a mineralogical standpoint, a mass of small rock fragment in 
which a very large variety of minerals are represented. Among these 
minerals two> greatly predominate, quartz and felspars. The quartz is 
so good as wholly unattacked by water. It is a simple chemical com¬ 
pound, and if it were dissolved by water it would not give rise to the 
kind of new bodies that we find in the alkalis. The felspar are com¬ 
paratively complex minerals and water acts on them quite vigorously 
breaking them up and forming new compounds. For the present pur¬ 
poses we may consider the plagioclase felspars only; these consist of 
alumina, lime, soda and silica, and are very abundant in our rocks. 
These felspars yield readily to the action of the natural waters, all of 
which contain greater or less quantities of carbonic acid taken up from 
both air and soil, and yield sodic carbonate, calcic carbonate, soluble 
silicates and free silicic acid, and leave as the end product, a hydrated 
