B. Silliman on the Mining Districts of Arizona. 295 
from the surface, which although hard, becomes reasonably good 
if constantly used. 
Saline or alkali incrustations.—Like all other regions of the 
It is the solution of these substances in the drainage waters 
which gives most of the springs in this section those deleterious 
properties known as alkalinity. It is to be observed that the 
water which will flow from tunnels and shafts, excavated here 
in the processes of mining, will possess little or none of the quali- 
ties belonging to the surface waters which dissolve away from 
every rain-fall the soluble saline matters that capillarity, aided 
y the powerful evaporation of a semi-tropical sun, concentrates 
upon the surface of the earth. This evil of bad water may there- 
fore be expected to disappear with the active prosecution of 
Mining enterprises. . E 
Climate and healthfulness.—Under a previous head the climate 
of the Colorado has been characterized. The San Francisco 
than can be found at the surface. 
d 
fases than this. I ascertained by enquiry from the physician at 
the military post that there were literally no climatic diseases 
‘hown on that portion of the Colorado.‘ Malaria is unknown, 
and fevers equally so; chronic diarrhea occurs rarely, and then 
8 traceable to causes independent of climate. This healthful- 
hess may be considered as nature’s compensation for some of the 
Privations incident to this fervid region. The effect upon the 
urinary organs, due to the use of the saline waters of the desert, 
disappears immediately upon the use of the river water or any 
Other pure water, and is always under the control of vegetable 
acids and of moderate doses of alcoliolic stimulants. . 
* See note (3), page 291. 
