CHARACTERISTICS AND DISTRIBUTION OF LAKES 559 
to be used for camp purposes ; at the northern end it is too saline and 
alkahne for human use, bift is used as drinking-water for cattle. 
Winnemucca Lake, 3875 feet above sea-level, 26 miles long, with 
an average breadth exceeding 3J miles, is also fed by the Truckee 
River, and has no outlet. As in the case of Pyramid Lake, nearly 
all the water-supply enters at the southern end, so that this portion 
is fresher than the northern. 
Humboldt Lake, about 4200 feet above sea-level, is but an 
expansion of the river that supplies it, and is held in check by 
an immense gravel embankment that was thrown completely across 
the valley by the currents of the former lake, at one time 500 
feet deep at this point. The embankment has been cut across by 
the overflow of the lake, but the breach has been partially filled during 
the past few years by an artificial dam, which has greatly increased 
the area of the lake. During the dry season the lake seldom 
overflows, and is then the limit of the great drainage system of 
the LIumboldt River ; but in winter and spring the waters escape 
southwards and, spreading out on the desert, form Mirage Lake. 
Farther south, in the northern part of the Carson Desert, they again 
expand and contribute to the formation of North Carson Lake. 
North and South Carson Lakes are shallow play a lakes in winter 
and spring, and in arid summers they evaporate to dryness. 
Walker Lake, 4147 feet above sea-level, is about 25 miles in 
length by 5 miles in breadth, and has an area of 95 square miles. 
A remarkably uniform depth of 224 feet was found over a large 
area in the central and western portions. 
Lake Tahoe,^ ''the gem of the Sierra,"' finds an outlet through 
Truckee Canon into Pyramid and Winnemucca Lakes, 2400 feet below. 
It is a mountain lake situated about 1000 feet above any traces of 
Lake Lahontan, at a height of 6234 feet above sea-level, and the 
boundary-line between California and Nevada passes through it in 
a north-to-south direction near its eastern shore, so that a little 
more than two-thirds of its area lies in California. The thirty-ninth 
parallel of latitude crosses the southern end of the lake, and the 
longitude is 120° W. The lake occupies an elevated valley on the 
humid forested summit range of the Sierra Nevada Mountains. The 
length is about 22 miles, the greatest width about 12 miles, and the 
area about 193 square miles. Comparatively few soundings have been 
made in the deeper water, and the greatest known depth is 1645 feet. 
Affluents are numerous, especially in summer, when the snow on the 
neighbouring mountains is melting rapidly, the largest being the Upper 
Truckee River; the outlet is also known as Truckee River. On 17th 
^ See C Juday, " Studies on some Mountain Lakes," Trans. Wisconsin Acad. Sci., 
Arts, cmd Letters, vol. xv. p. 790, 1907. 
