2 8 
Colorado Experiment Station 
Sodic sulfate 
Calcic sulfate 
Sodic chlorid 
31.780 
0.928 
6.691 
39.706 
20.896 
Sodic carbonate 
Organic matter 
100.000 
The last two samples were met with in the section south and west 
of the Rio Grande. The explanations offered are the only ones pos¬ 
sible in this case. These are, so far as I know, of very limited occur¬ 
rence, and could not in any event modify in any important manner the 
character of the Rio Grande waters though they might be local fac¬ 
tors in the unproductiveness of the soil. 
THE PRODUCTION OF SODIC CARBONATE FROM THE FELSPARS 
While there are differences between the composition of the Rio 
Grande water and the drain- and (ground-waters, and the extracts of 
the soils presented, there are also persistent resemblances which we 
did not find in our stuly of these subjects in the neighborhood of Fort 
Collins and other sections. 
In an article entitled “The Significance of Silicic. Acid in the 
Mountain Waters, etc.,”* I pointed out that the characteristic results 
of the action of natural waters on the felspars is the production of a 
solution carrying principally the carbonates of the alkaline earths and 
alkalis with some sulfates and chlorids. Of the carbonates of the al¬ 
kalis, the carbonate of soda occurs in excessively large amounts in 
proportion to the amount of soda in the felspar; in other words, the 
amounts of lime and soda taken into solution indicate the predomi¬ 
nant decomposition of the soda-lime felspars. This characteristic in 
the composition of the salts in solution persists almost wholly unmodi¬ 
fied in the Rio Grande water in spite of the long distance that it flows 
through the valley, but it also persists in the drain and ground waters 
in a marked degree with only one pronounced modification, namely, 
the increase of sulfates; the ground-water, for instance, from SE. 34 , 
sec. 23, T. 38 N., R. 8 E., or the drain-water from the Parma Land 
Company’s ditch, or that taken from drain in SE. Ft, sec. 24, T. 4° 
N., R. 8 E., might be taken for mountain waters, except for the large 
amounts of calcic sulfate present, which reach a maximum of 55.6 
percent. It is not easily explicable why sodic carbonate does not ap¬ 
pear in this analysis unless it be due to the abundance of calcic and 
magnesic oxids, but the appearance of this salt in ground- and drain- 
waters, as well as in river waters, is to be expected, except under such 
conditions as are indicated in the case just given. 
Attention is called to these facts in this place, not only because 
these ground- and drain-waters present these characters, but also for 
*Am. Jour, of Sc., Vol. XVI. Aug., 1903, pp. 169-184. 
