164 
METEOROLOGICAL AND 
P. M. the same; at half -past 3 it stood at 62^ I hove 
to, and got bottom in 145 fathoms; Cape Point SE., 
Lion's Head NE. Here the difference was only 3°, and 
the water was 45 fathoms deeper than in the former expe- 
riment. 
On coming into soundings in the English Channel, I 
found 5° difference of temperature. 
If there are banks in the ocean which approach as near 
to the surface as 140 fathoms, they will be indicated by the 
fall of the thermometer in the surface-water ; and all na- 
vigators will immediately perceive the advantage of deter- 
mining their latitudes and longitudes by means of such 
banks, as from them ships may frequently be enabled to 
ascertain their situations with as much certainty as from 
land. 
2. Temperature of the Ocean at great depths. 
The following experiment was made to determine the 
temperature of the ocean at a considerable depth. The 
thermometer was inclosed in the middle of six cases, all of 
tin, except the outer one, which was of wood ; each case 
had a valve below and at top, both opening up- 
wards, in this manner; the valves remaining 
open when descending, but closing when coming 
up. The four inside cases were separated from 
each other about a quarter of an inch all round, 
allowing the water to pass freely between them. 
The fifth case was distant from the one immediately inside 
of it about half an inch, and the space between filled up with 
tallow. The outer case of all, or sixth case, was of wood, 
