NORTHWESTERN LAKES OF THE UNITED STATES. 
85 
4,800 feet) high, but the west shore rises only a few meters and forms a part of 
Rathdrum Prairie. The main or southern part of the lake is 8.1 km. (5 miles) long 
in a northeast line and 3 km. wide (1.8 miles). At the northeast corner a shallow 
neck of the lake extends 3.75 km. (2| miles) due north. The elevation of the sur- 
face of the lake is 683.5 m. (2,242 feet) and its greatest depth is 57 m. (187 feet), 
which depth is very constant throughout the north half of the main part of the 
lake. Here over 40 soundings were made, covering an area of about 4 km. 2 , and 
in no case did the depth vary as much as a meter. 
The temperature of the water during July at the surface was 16.9° C., with a 
distinct thermocline between 8 (16.7° C.) and 20 m. (6.1° C.), while the thermometer 
showed 4.7° C. at the bottom. 
The lake has a small outlet controlled by a dam, and water is pumped from the 
lake for irrigation, but the level is not materially changed. 
Wright Lake is a small pond that has been enlarged by a 6-m. (20-foot) dam 
until it is 1 km. long by f km. wide. It lies about \ km. west of Hayden Lake on 
Mr. Wright’s farm. According to Mr. Wright it was stocked with large-mouthed 
black bass ( Micropterus salmoides ) and cutthroat trout ( Salmo clarkii) in 1896. 
The bass thrived and many have been caught, but only a few trout have been taken. 
This fact is mentioned here because it was due to a freshet that the bass were washed 
from Wright Lake into Hayden Lake, and this species was introduced with the cut- 
throat trout for which the lake was noted. To-day Hayden Lake offers excellent 
bass fishing especially in the shallow area and in the bay near the dam. Whether 
these bass have caused a decrease in the number of trout or not is a very interesting 
question and one not easily answered. From all reports the trout fishing is not as 
good as a few years back, but where is the lake within 40 miles of a large city, with 
direct rail connection and a good hotel, where the trout fishing has not decreased ? 
There are still large numbers of cutthroat trout caught with flies in the early 
summer and by trolling with a small spoon just below the thermocline during the 
late summer. 
Recent correspondence (1921) with several fishermen of the section seems to 
indicate that both the trout and the bass continue to thrive. It should be noted 
that a very active sportsmen’s club has helped by keeping the lake well stocked with 
trout from its hatchery. 
On August 25, 1912, the Crustacea were well distributed throughout Hayden 
Lake, resembling the distribution in Lake Coeur d’Alene, with a smaller portion of 
material in the epilimnion than in the hypolimnion. Only 32 per cent were above the 
thermocline. A rather peculiar thermocline was found, in that it was a stratum only 
1 m. in thickness between 10 and 11m. Cyclops bicuspidatus was the predominant 
crustacean, and it was abundant throughout the entire depth of the lake. The 
maximum number per cubic meter of water was in the 10-15 m. stratum. Daphnia 
hyalina was found in small numbers at all depths. Bosmina longirostris var. brevi- 
cornis was confined to the upper 25 m. of the lake, the maximum number per cubic 
meter of water being in the 0-5 m. stratum. Diapkanosoma leuchtenbergianum was 
above the thermoclifie. 
Nauplii were very prominent in Hayden Lake, comprising about 47 per cent of 
the total number of Crustacea. They were found at all depths in the lake, but 52 
