J. LeConie—Hatinct Volcanoes about Lake Mono. 43 
Pacific ocean. King has shown that the Nevada basin was at 
the same time occupied by a vast irregular sheet of nearly 
equal extent, stretching southward as faras Columbus, Nevada. 
Pyramid, Winnemucea, Carson, Humboldt, and Walker Lakes, 
are the concentrated residues of this great lake. Lake Mono also, 
we have seen, at the same time, was a great sheet of water, 
whether connected with the other or not is not known. There 
has been therefore an increasing dryness of climate in that re- 
gion since the Champlain. Is it still progressing, or has it 
eached its maximum? This is an important question for the 
~~ States 
my observations on Lake Mono, I have no doubt that 
its Listed; at the time of my visit, was rising and had been —e 
for ten or fifteen years. The evidence is as follows: Aroun 
the margin of the lake I found everywhere old fences of sheep 
corrals and old trails submerged many feet deep. While visit- 
ing the island I found the vegetation of the island, sage brush 
Artemisia tridentata), and grease wood (Sarcobatus vermicu- 
latus), submerged in five feet of water, and of course killed. 
idents about the lake state that the waters have risen ten to 
twelve feet in ten or fifteen years. I might be disposed to 
doubt these observations if the same phonoaninn had not been 
observed in other lakes in the same dry region. Salt Lake is 
known to have risen ten to fourteen feet in twenty five years 
and submerged large tracts on its flat margins, and the water by 
analysis is far less salt than formerly. Pyramid Lake, accord- 
ing to King, has risen nine feet, and Winnemucca Lake twenty- 
two feet in only four years—1867-1871. The same is said ” 
be true of Walker Lake and of Owen Lake. 
The cause of this is evidently increase of rain-fall and snow- 
ae chiefly the latter. In this connection it may be well to 
ention an additional evidence of -ie snow-fall in the 
ign 
glacieret is not only — hard against the motaine but the 
* This Journal, II, v, 325. 
