The: Waters of the Rio Grande 41 
time of taking the last sample, covered with water. This was the case 
to such an extent that, had I not been accompanied by a person 
thoroughly acquainted with the ground, I would not have ventured to 
try to approach the lake. 
An examination of these analyses makes evident the fact that the 
solids held in solution differ materially from those of any water so 
far presented. They differ from the river waters in containing less 
silicic acid, less lime and magnesia, more chlorin, a£ much or more 
carbonic acid, about the same amount of sulfuric acid and very much 
more potassic and sodic oxids. This is particularly noticeable in the case 
of the potassic oxid. The differences are not such as we find in the 
drain- or ground-waters, nor do they correspond to the changes that 
we might expect as due to evaporation of the river waters. Evapo¬ 
ration is without doubt an important factor in the case. The evapo¬ 
ration from the lake surface is probably not less than 60 inches annu¬ 
ally and must effect some changes, but we find the sulfuric acid at the 
time of low water less than in the river waters. The concentration of 
these waters is very far from the point at which ‘any sulfates would 
separate due to this cause. The total solids in the lake water amount 
to, approximately, 8 or 12 times as much as we find in the river water. 
The potassic oxid is from 4 to 6 times as high in the residue from the 
lake-water as in that from the river-water. 
There is, further, no relation between the lake and artesian 
waters. The differences mentioned above are even more strongly pro- 
nouncd in this case than in that of th e river waters. This would be a 
natural inference as the source of the lake- and river-waters is evi¬ 
dently the waters supplied directly by the mountain streams, and still 
it is altogether possible that the lake-water may be directly supplied 
from the artesian basin, as I believe some of the springs in this sec¬ 
tion of the valley to be, the Washington Springs for instance. There 
are artesian wells on the east side of the lake and very close to it. The 
water is white, tastes distinctly of hydrogen sulfide but is an agree¬ 
able, potable water. The water furnished by the nearest well that I 
know of on the west side of the lake, furnishes a tinted water. These 
wells may, indeed almost certainly do, tap different flows. The soda 
lakes are close to the San Luis lake on the east and south. I hold 
that these soda deposits owe their origin to the brown artesian waters 
which come to the surface at these points and are evaporated. Such 
an explanation is clearly not applicable to the water of the San Luis 
lake. These relations are pointed out because the statement of our 
work on the waters of the valley would not be complete without ref¬ 
erence to it, and also for the better reason that the water presents in¬ 
teresting questions. 
