( 
108 Mr De La Beche on the Depth and 
was perceived at the surface. At the depth of 15 fathoms, a 
current carried the thermometer to the west ; and when I 
had let out 10 fathoms more of cord, I perceived that another 
current carried it almost as rapidly to the east. None of these, 
however, lasted long, for, on letting out 12 fathoms more, the 
thermometer ceased to be influenced by any current. The boat- 
men informed me, that these currents were very irregular, and 
had all sorts of directions. 
The self-registering thermometer which I used, was similar 
to those employed on the late Arctic Expedition. About 2 lb. 
of lead was always added for great depths, in order to make it 
descend vertically. 
In observing the soundings, I at first allowed the lead to 
descend, and having raised it, I made it redescend two or three 
times, in order to ascertain that I had reached the bottom. 
The thermometer was then substituted in place of the lead ; and 
after being attached to the sounding line, I sunk it to within 
half a fathom of the bottom in deep water, and a quarter of a 
fathom in smaller depths, — a precaution which was necessary, in 
order to prevent it from striking against the ground. 
TABLE of the Depths and Temperatures of the Lake of Ge- 
neva^ in the different places indicated on the Map (Plate II.) 
which accompanies this paper. 
Dates. 
■ . 1 
Depth. 
Temp. 
Dates. 
Depth. 
Temp. 
1819. 
I 
j 
Path. 
' 1 
Fahr. 
1819. 
Path. 
Fahr. 
67° 
Sept. 
From Belle- 
^ 26 
46° 
66 
15. 
rive to Ge- 
20i 
52 
Sept. 
41 
65 
neva. 
5 
65 
15. 
From Ge- 
5 
65 
67 
neva to -< 
Genthod, 
1 
10 
64 
62 
58 
16. 
From Gene- 
va to Belle- 
f Si 
6 
11 
64 
63 
58 
15 
54 
rive. 
12 
58 
18 
53 
^ 14 
55 
From Gen- i 
r 24 
60 
20. 
Prom Belle- 
23 
45 
thod to 
45 
rive to Co- - 
34 
44 
Bellerive, i 
1 m 
45 
pet. 
30 
45 
1 
1 s 
62 
