40 
Colorado Experiment Station 
sumably the same as the preceding, contains 29 grains to the gallon 
and 9.3 grains of sodic carbonate, whereas at 750 feet the water in the 
eastern part of this area carries 104.3 grains, of which 99 grains or 94 
percent is sodic carbonate. The calcic and magnesic sulfates are al¬ 
most wanting in the effloresced alkalis of this section, and also in the 
soils. I do not recall a single section of soil in which I have found 
the usual layer of marl consisting of a mixture of calcic carbonate and 
sulfate. If we find any, it is the carbonate. The analysis of the soil 
made by extracting it with strong hydrochloric acid, shows that there 
can be but little sulfate of lime even if all the sulfuric acid present were 
combined with lime. It is improbable that any of it is so combined, 
owing to the presence of sodic carbonate. An analysis of one of these 
soils, taken in a very strongly alkalied section, shows only 0.363 per¬ 
cent of sulfuric acid, which would form but enough calcic sulfate to 
make a scant 0.6 percent of the soil. The analysis shows that there is 
carbonic acid enough present to combine with more than three-fourths 
of all the lime present, leaving 15 percent of soluble silicic acid to satisfy 
about 13 percent of bases which the hydrochloric acid took into solu¬ 
tion. At the same time we are quite certain that some of these bases 
were present in still other forms, ferric hydrate, for instance. 
Judging from the above sample of soil taken from as strongly an 
alkalied area as there is in the section, the total amount of calcic sulfate 
which may possibly have existed in an acre-foot of this soil is about 
12 tons, but which we do not think was there at all, is not large com¬ 
pared with the amount existing as gypsum, which we can see in the 
soils from other parts of Colorado. There are some sections where 
we find layers of calcic sulfate 3 or more inches thick. A sample of 
subsoil from another part of the State taken to represent 2 feet of the 
subsoil, carried 120 tons of calcic sulfate to the acre-foot. 
The composition of the alkalis varies locally but it is usually quite 
persistent in its character, for instance, in some sections the calcic and 
magnesic sulfates make up as much as 50 percent of the effloresced 
mass while sodic sulfate, chlorid, and carbonate make up the rest, of 
these the sodic sulfate usually predominates sometimes, however, the 
chlorid predominates, but this occurs rarely with us. 
This whole section of approximately 5,000 square miles is char¬ 
acterized by the absence of calcic and magnesic sulfates in the efflores¬ 
cences found on the surface of the soil, the predominant salt being 
sodic sulfate. This statement also applies to the 800 square miles of 
the northern section of which we have spoken in the preceding para¬ 
graph. In this section the sulfate is associated with the carbonate, 
which is not only present with it but even becomes abundant enough 
to be injurious. The following analysis of an effloresced alkali taken 
