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waves, but is generally smooth and glassy. Near its north shore 
there are springs which have produced extensive deposits of 
tufa, some of which rise several feet above the surface in forms 
resembling gigantic fungi. 
There are numerous islands in this lake, two of which are of con- 
siderable size, the largest being two and a-half miles long, from 
north to south, and the other about half a mile in length, from 
east to west. These, as well as a group of smaller islets lying to 
the north, are entirely composed of volcanic materials. 
On the north-eastern corner of the larger island are extensive 
hot springs and steam-jets, covering an area of some thirty acres, 
and extending into the lake. The escape of steam and hot gases 
from so many hundreds of vents is attended with much noise, 
and the sides of the orifices of many of the fumaroles are in- 
crusted with a reddish-brown substance, which is probably chloride 
of iron. In the neighbourhood of these springs there is a slight 
smell of sulphurous acid, but no free sulphur is deposited. Some 
of them furnish a copious supply of boiling water, large quantities 
of which enter the lake, and so perceptibly raise its tempera- 
ture for a considerable distance around. Much gas and steam 
escape from a fissure caused by the sinking of a portion of the 
crust, while on the eastern part of the island are two well-defined 
craters, now filled with water. 
Mono Lake is, during the summer, the resort of myriads of 
gulls and other aquatic birds, which are most numerous during 
the breeding season, but the water is believed to be entirely 
destitute of life, with the exception of a small crustacean, Artemia 
fertilise nearly related to the so-called brine shrimp ( Artemia 
salina) found in the strong brine of the salt pans on European 
coasts, and the Koo-chah-bee of the Indians, a whitish larva, 
occurring in immense quantities, and which is much esteemed 
by them as an article of food. 
Stretching south of the lake is a chain of extinct volcanoes, 
presenting the form of truncated cones, of which the generally 
steep sides are covered with ashes and other loose materials. 
Obsidian and pumice are abundant on the surface of these 
cones, and also cover the plains at their base. 
Owen’s Valley is a narrow basin lying south of Mono Lake, 
and running nearly north and south for a distance of about 140 
miles. Its average width may be taken at ten miles. It is 
bounded along its western edge by the Sierra Nevada, which in 
this portion of its course presents an almost unbroken wall, of 
which the highest peak, opposite Owen’s Lake, reaches an ele- 
vation of 15,000 feet. No pass crosses it at a less height than 
11,000 feet, and near the lake-shore the descent from the sum- 
mit to the valley beneath must have an average inclination of at 
least 1,000 feet per mile, the distance being from ten to eleven. 
