SALMON INVESTIGATIONS IN IDAHO IN 1895. 
157 
level' tract, densely covered with a growth of small Murray pines, tlirough whicli a 
forest lire lias recently raged, killing nearly every tree. 
A fairly good wagon road extends from Salmon Valley u]) this side of the loke 
to the inlet. The outlet of the lake is through a heavily wooded valley, where tke 
Murray pine is the prevailing tree. 
At the upper end of Alturas Lake is the narrow valley of the inlet which will he 
described more fully later on. 
Depth . — A great many soundings were made in this lake, the majority of which 
are indicated on the accompanying map. Six principal lines were run across the lake 
and soundings taken at every 100 strokes with the oars, that is, about every 400 feet. 
As may be seen from the map, the lake is most shallow and grows deep most gradu- 
ally on the right side. The left side becomes deep very close to shore. At the upper 
and lower ends, alsi>, the depth increases quite rapidly. The greatest depth found was 
157.t feet, which was near the middle of the left side of the lake. There seems to be 
here a basin of considerable extent, ranging in depth from I.'jO to 1574 feet. 
The left bank is rocky and in places precipitous; the lower end and the right side 
are covered with coarse gravel, while at the upper end the bottom is of fine sand as 
far out as bottom can be seen. 
Tlie water of the lake is very pure and clear, and, when tlie surface is not dis- 
turbed, one can see bottom at a depth of 40 feet and cau detect the presence of small 
fishes at a depth of 30 feet or more. 
Temperature . — The water of this lake is very cold and does not differ appreciably 
from that of Pettit Lake. Our camp was not at any time so situated as to make 
it practicable for vis to take temperature observations on Alturas Lake at regular 
intervals. The surface temperature at 9.30 a. m., August 10, was 61°, and at 4 j>. m. 
was 63°. It did not vary greatly from these figures during the last half of July 
and up to the 22d of August. At that date it began to grow gradually colder and 
was down to about 59° by Seivtember 22. The bottom temperature was found to be 
from 3° to 8° colder than that at the surface, varying with the vlepth. The lowest 
temperature was found to be 54°, at a depth of 157 feet. 
Vegetation in the lalce . — -In most places this lake is comparatively free from plant 
life. While there is considerable bottom vegetation in some places it does not anywhere 
reach the surface, except in a limited area in shallow water at the head of the lake. 
About the mouth of the inlet, beginning on the sandy bottom in water 4 or 5 feet 
deep and 10 to 20 feet from shore, and continuing out to a vlepth of 60 feet or more, is 
a thick, rank growth of vegetation, the principal species being Fotaynogeton perfoHatus 
lanceolatus, Potamogeton zosterafoUuSj Potamogeton ampUfoUuH., a species oi‘ Mgriophgl- 
lum, a Nitella., and a Chara. This growth seems to extend entirely across the upper 
end of the lake at varying distances from the shore, but is always confinevl to the 
fine sand bottom, and apparently between 4 feet and about 60 feet in depth. More 
extended observations than we were able to carry on will probably show that other 
parts of the lake possess similar patches of vegetation, particularly along the right 
side. These masses of vegetation fill, of course, an important place in the biology of 
the lake. Harboring, as they do, the great bulk of the food of most of the species 
of fishes which live in the lake, here will be found minnows, suckers, and young 
Salmonidee in greatest abundance. Indeed, nowhere else in the lake did we find fishes 
of any kind in any considerable numbers. 
