Alkalis In Colorado 
7 
silicate of alumina. This is insoluble in water while the other pro¬ 
ducts are soluble. This presents the main features of this alteration 
process. If there be only a moderate amount of water, the decom¬ 
position may go on and the products formed remain in the soil or be 
only partially removed. This is the case in our semi-arid areas. 
These products of the alteration of the rocks remain in the soil or are 
removed only a little way from where they were formed only to be 
left, by the evaporation of the water, in some other nearby place, where 
they become so abundant as to form white incrustations. While this 
is true, it is very far from presenting all that we know about these 
changes, in fact, we are compelled to go further in the explanation of 
the facts as we find them. According to what we have said, these 
incrustations should be composed of sodic carbonate, calcic carbonate, 
some silicates and silicic acid. It is only occasionally that we find 
these deposits to be made up of carbonate; as a rule, we find them to 
be sulfates, and while the sulfates of soda and lime make up by far the 
larger part of our alkalis, the sulfate of magnesia and sodic chlorid 
are so good as always present in varying quantities. That some car¬ 
bonate should be present would seem to be inevitable, for the solutions 
furnished by the decomposition of the felspars are in the first place 
carbonates and the changes that are made in these solutions may not 
always be quite complete; besides, the felspars are actually every¬ 
where in our rocks and soils and are all the time being acted on by car¬ 
bonated water. The calcic and sodic carbonates are partially or wholly 
changed into sulfates. These salts contain a different acid from the 
carbonates, which got their acid from the water which effected the de¬ 
composition of the minerals. The gypsum in the soil is the agent that 
most commonly brings about this change. We have also added mag¬ 
nesia to the list. 
If we take fresh felspar, grind it up very finely, treat it with 
water containing carbonic acid, say for three weeks, and examine this 
water, we will not only find that it contains the carbonates of lirne 
and soda with some silica, but also both sulfates and chlorids, not so 
much as carbonates, but enough to show that these minerals them¬ 
selves contain some sulfates and chlorids. If every rock mass of our 
mountains contains some chlorids and some sulfates ready formed we 
need scarcely puzzle ourselves in looking for the source of the chlorids 
and sulfates that we find so generally distributed. It won’t help us any 
to go further back in the history of these chlorids, for our purposes, 
it suffices that they are present in the rocks of our mountains and in 
the waters that flow from them- to the plains. The same is true of the 
sulfates, and why should we look further? Here is a source suffi¬ 
cient to. supply as much chlorin, for instance, as we may be called on 
to account for. If we need more sulfuric acid, there is a source near 
