162 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
smaller than Altuvas Lake and is more irregular in outline. The greatest length is 
about 1.1 miles, while the greatest width is about half a mile. The upper half of the 
lake has the sides relatively parallel, but the lower half is quite irregular in outline. 
The outlet is at the lower left-hand corner; on the right of this is a considerable 
peninsula projecting into the lake. At its outer end it turns toward the right shore 
and has very much the shai)e of a fish-hook, inclosing a> small shallow bay. 
Like Alturas Lake, this lake is also of glacial origin and lies between two immense 
lateral moraines. The ridge on the right is apparently composed entirely of morainic 
material. At the upper end of the lake this ridge is 200 or 300 feet above the surface 
of the water, but it becomes gradually lower as it approaches the Salmon Eiver 
Valley, until opposite the lower end of the lake it is perhaps not over 50 feet high. 
The ridge bounding the lake on the north rises rather abruptly, attains a height 
of 500 or 600 feet, and probably pos.'-esses a granite axis or core. To the left, this 
ridge is continuous above with JMount Parks, and below, it extends far out into Salmon 
Liver Valley. The terminal moraine extending across the canyon at the foot of the lake 
has a broken, uneven surface, and the outlet through much of its course possesses many 
rapids. The ridge on the left and the upper end of the one on the right are covered with 
a heavy growth of conifers, chiefly Murray pine and Douglas fir. The Murray iiine 
grows most abundantly near the lake and on the lower slopes, while the fir is rarely 
found on the lake shore, it being found chiefly somewhat above the lake. At the head 
of the lake is a narrow valley or canyon densely wooded throughout. Lear the lake 
it is level and somcAvhat marshy in places and supports a heavy growth of Murray 
pine, Douglas fir, and white spruce. 
Pettit Lake is quite deep. Lines of soundings were run across it in various direc- 
tions and the depths found are indicated on the accompanying map. As will be 
noticed, this lake, like Alturas, has its greatest depth near the ui)per end and toward 
the left shore. That part of the lake reaches a maximum depth of 175 feet. The 
lower third of the lake is comparatively shallow, a greater depth than 23 feet not 
being found. The narrow bay at the lower end on the right side is still more shallow, 
7^ feet being the greatest depth found. 
At the head of the lake a fine sand bottom extends out until at least a depth 
of 40 feet is reached. There are also some areas of white sand bottom along the right 
side, but most of this portion is covered with small granite rocks. The lower half of 
the lake, particularly the narrow shallow bay, has a sand bottom except along the 
immediate shore, where it is usually rocky. The left shore of the lake is usually 
rocky and the bottom descends very abruptly, a depth of 50 feet or more being reached 
within a few feet of shoi'e. 
There seems to be less vegetation in this than in Alturas Lake. Small patches 
were observed at various ])laces in relatively shallow water, but we did not deterndne 
the character of the bottom in the deeper places, so do not know whether there is 
any vegetation there. The water is very clear and pure. Where the bottom is of 
white sand it can be clearly seen at a depth of 40 feet, but in the deep parts of the 
lake the water appears very dark when viewed from the boat. 
Temperature . — The water of this lake is very cold. Surface temperatures were 
taken at irregular intervals from July 26 to Aiigust 12, after A\diich the temperature of 
the surface near our camp was taken regularly three times daily. The results are set 
forth in the tabular statements which follow. The bottom temperature in the deei)er 
