1880.] 
65 
[Nichols. 
Lake Survey in Lake Superior which, by the kindness of the 
Chief of Engineers, U. S. A., I am able to introduce here. See 
Table V. The instruments employed by the Lake Survey were 
Casella dee j)sea thermometers, and the reading of 33°.4 on August 
15 is supposed to be erroneous and due to an accidental displace- 
ment of the index. The same may be true of the reading 36°. 8 
on August 18. Omitting these, it would seem that the frequently 
observed 38°. 8 F. (3°. 8 C.), in one case 38°.T, is probably the tem- 
perature of greatest density of the lake water. 
Table V. Observations to determine Surface and Bottom 
Temperature of Lake Superior, made in 1871, by the 
U. S. Lake Survey. 
Date. 
Latitude. 
Longitude. 
Depth 
in 
Fath’ms 
Temperature at 
Surface in deg’s 
Fahr. Cent. 
Temperature at 
Bottom, in deg’s 
Fahr, Cent. 
August 7 
46° 53' 
86° 43' 
127 
56.5 
13.6 
38.8 
3.8 
to 
to 
129 
56.0 
13.3 
3 8. *8 
3.8 
47° 23' 
86° 15' 
121 
53.0 
11.7 
39.1 
3.9 
131 
'50.1 
10.1 
38.8 
3.8 
74 
50.8 
10.4 
38.8 
3.8 
August 11 
48° 18' 
86° 15' 
59 
55.8 
13.2 
41.3 
5.2 
August 15 
o 
o 
oo 
87° 3' 
105 
49.7 
9.8 
39.0 
3.9 
to 
to 
121 
49.5 
9.7 
39.2 
4.0 
47° 45' 
87° 6' 
168 
49.2 
9.5 
39.0 
3.9 
116 
50.2 
10.1 
39.3 
4.1 
136 
52.2 
11.2 
38.9 
3.8 
158 
52.9 
11.6 
33.4? 
0.8 
August 18 
48°' 9' 
88° 15' 
47 
51.8 
11.0 
36.8 
2.7 
to 
to 
129 
52.7 
11.5 
38.9 
3.8 
47° 36' 
87° 42' 
336 
52.3 
11.3 
38.8 
3.8 
- 
134 
50.1 
10.1 
38.9 
3.8 
82 
51.5 
10.8 
39.0 
3.9 
August 22 
Near Copp 
er Harbor. 
148 
_ 

38.7 
3.7 
ib 
51.3 
10.7 
39.7 
4.3 
61 
55.3 
12.9 
39.2 
4.0 
August 29 
48° 42' 
87° 47' 
73 
55.0 
12.8 
38.9 
3.8 
proceedings b. s. N. H. VOL. XXI. 
6 
AUGUST, 1881. 
