B, Silliman on the Mining Districts of Arizona. 298 
drifting sands, but in about an hour the violence of the storm 
abated, vivid lightening and powerful thunder to the east of us 
succeeded, and, an hour later, a dash of rain for a few moments, 
just the outer skirt of the thunder storm, but enough to drive 
me to seek the shelter of the ambulance. 
At Fort Mojave we experienced another similar wind-storm 
with the temperature over 100°, occasioning more annoyance 
from the scorching effects of the powerful hot wind. ; 
The officers at Fort Mojave assured us that these hot wind- 
storms blow sometimes with great violence for a whole week, 
When it is impossible to go abroad; men and animals being 
liable to be lost if overtaken on the open desert, as it is then no 
longer possible to observe the way, gain a shelter, or find water, 
the latter difticult enough under the best circumstances.” 
Any notice here of the geology of the Mojave Desert, would 
extend this paper beyond its proper limits. 
San Francisco Disrricr. 
Situation and approach.—The San Francisco Mining District is 
larly wild and fantastic outline of its bounding mountains and 
intermediate ridges; he learns with surprise that the bold and 
Serrated peaks stretching from east to west, and rising, now in 
delicate needles, and again prolonged in acute ridges, are the 
outcrops of gigantic quartz lodes, among which are seen con- 
Splcuously the Moss lode on the north,—the Skinner and Par- 
Sons on the south. The general aspect of these outcrops is dif- 
ferent from that of those seen in any other portion of the 
