‘‘Black Alkali'’ in the San Luis Valley 
ii 
Mosca, nor with the mill well or the railroad well, or the town well 
at Hooper. These waters are brown, strongly alkaline and contain 
sulfur; they even smell of it. The older residents of the section 
well remember that there was a well near the present railroad sta¬ 
tion of McGinty that was called the soda well, because, so it was 
said, they could use this water instead of baking powder for 
making light bread. I never believed this story, but it shows that 
the water was remarkable and that the citizens were resourceful 
in presenting the advantages of the country. This well is now 
closed. 
The presence of gas in this district is, in some instances, 
abundant enough to furnish light and fuel for the houses of the 
owners. 
The conditions that cause the waters to be brown and to carry 
sodic carbonate in such easily recognizable quantities have pro¬ 
duced the difficulties that threatened the district from the be¬ 
ginning and which the practice of sub-irrigation has made real. 
All of the ground waters that I have examined from Center 
east to Hooper and from Hooper, I may add from Moffat, south 
to below McGinty, carry sodic carbonate in solution. In the case 
of the brown waters, there is present in the strata from which the 
waters come, enough humus which is soluble in sodic carbonate, 
to impart the brown color. Some of the wells near the edge of this 
area, especially shallow wells, carry sodic carbonate, though they 
are only slightly or not at all colored. The characteristic of our 
mountain waters is that they carry only a small amount of sub¬ 
stances in solution, and these substances are silicic acid, the car¬ 
bonate of lime, and the carbonate of soda. The silicic acid and 
the carbonate of lime can be removed easily, but not the carbonate 
of soda. This salt is not removed to any great extent when its 
solution passes through the soil, nor is it thrown out of solution by 
any agent or by the evaporation of its solution as the lime may 
be by the escape of carbonic acid on exposure to the air. 
The artesian waters along and south of the Rio Grande are 
excellent waters for all domestic purposes; they carry carbonate 
of soda with the carbonate of lime and silica just as the waters of 
the mountain streams do and in only slightly greater quantities. 
This is not true of the brown waters, for they carry almost nothing 
besides the sodic carbonate and they carry a great deal of this salt. 
The mill well at Mosca, for instance, carries \y 2 pounds of sodic 
carbonate in every 1,000 pounds of water and only 1-10 of a pound 
of all other solids taken together. A barrel of this water weighs 
a trifle over 300 pounds and this well will furnish a great many 
barrels in an hour. 
