626 
MR. J. PRESTWICH ON SUBMARINE TEMPERATURES. 
a strong pressure on different substances, and which he has made known in the 
‘Memoirs of the Academy of St, Petersburg’ (vi. serie, Sc. Math. Ph. et Natur., t. ii. 
p. 595, 1832). It is there mentioned that a pressure of 100 atmospheres caused the 
thermometer to rise about 20 o, 5, without the temperature having altered in the least, 
as was shown by a second thermometer which was protected from pressure by a brass 
cylinder.” 
Lenz proceeds to remark that it necessarily follows that thermometrographs (although 
in such instruments the effect would be much less owing to their form of construction) 
exposed in the sea to pressures of 100 to 200 atmospheres must give too high a 
reading, and that the circumstance of the indications in so many deep soundings 
remaining uniform, or sometimes increasing with the depth, proves the influence of 
compression. 
Reviewing the data furnished by different observers and by himself, and assigning to 
them, if not an actual, at all events a relative and comparative value for corre- 
sponding depths, Lenz notices the circumstance that they all point to the existence 
of a belt of water at and near the equator cooler than at a short distance to the 
north and south of it; and in illustration of this he takes the consecutive series of 
observations at nearly the same depths made by Kotzebue in 1815-1818, at short 
distances apart over a great length of the Atlantic ; and he gives a Table, of which the 
following is an abstract : — 
Zones of 
latitude. 
North Atlantic. 
South Atlantic. 
Mean 
depth. 
Mean 
temperature. 
Mean 
depth. 
Mean 
temperature. 
feet. 
°F. 
feet. 
°F. 
0 to 3 
435 
58-2 
480 
57 
3 „ 6 
460 
57-8 
405 
56-4 
6 „ 9 
400 
58 
351 
61-5 
9 „ 12 
390 
59-4 
426 
62-7 
12 „ 15 
390 
58-2 
351 
60-8 
15 „ 18 
408 
66-7 
305 
60-3 
18 „ 21 
468 
68-2 
378 
61-7 
21 „ 24 
414 
69-2 
420 
63-2 
24 „ 27 
432 
69 
27 „ 30 
403 
65-7 
30 „ 33 
390 
60 
33 „ 36 
447 
62-2 
36 „ 39 
418 
61-2 
39 „ 42 
438 
58-5 
45 „ 48 
458 
53-6 
This, he observes, shows a rapid rise of the isothermal planes in approaching the 
equator; and taking a definite isotherm of 14 0, 5 C., he gives the following diagram, in 
which he shows that this plane, which in lat. 45° to 48° N. lies at a depth of 350 feet, 
sinks gradually to 640 feet in lat. 23° to 26°, and then, rising more abruptly as it 
