of Land on the Temperature of the Sea. 339 
one mile from the shore, it had fallen as low as 64 degrees, 
and continued from 64 to 65 degrees, between Cape Manoel 
and Goree. Cape Verd is situated nearly at equal distances, 
exceeding 70 miles, from the mouths of the Senegal and Gam- 
bia, the one being to the north and the other to the south. It 
is probable that the water of both these rivers is always colder 
at their entrance into the sea, than the ocean temperature of 
the parallel; that of the Gambia certainly was so at that sea- 
‘son, but it was not so cold as the sea in the vicinity of Cape 
Verd, as on approaching the entrance of the Gambia, the tem- 
perature of the surface rose to 67°°5, and varied in the river 
itself at different hours from 66° to 67°°5; and at the depth 
of 36 feet, being within six feet of the bottom, a self-registering 
thermometer indicated at high water less than a degree colder 
than the surface. The coast in the neighbourhood of Cape 
Verd is every where low and sandy, and is covered with trees 
to the water’s edge. Such, indeed, is the general character of 
the shores of western Africa, with the exception of Cape Sierra 
Leone; but at no other part of the coast was the diminution 
of the temperature of the water, on approaching the land, so 
great, as in the instance which has been mentioned. Between 
the Gambia and Sierra Leone are a succession of rivers, ori- 
ginating in land of less elevation than the Senegal and Gambia, 
and much exceeding them in the temperature of the waters 
which they convey into the ocean; in the mid-channel of the 
Rio Grande, at a few miles from its mouth, the surface was 
never less than 74°, and occasionally as high as 77°*5, and at 
the depth of 30 or 40 feet was less than a degree colder than 
the surface. At the entrance of the River Noonez the surface- 
water was 77°°5, and at that of the Rokelle 80°. To the south 
of the Rokelle, and from thence to the extremity of the Gulf 
of Guinea, the coast is swept by a current of considerable ra- 
pidity, which renders the cooling effect of the land less appa- 
rent; but in the bays of the coast, where the current sweeps 
from point to point, and leaves still water in the inside, a diffe- 
rence is commonly found amounting to three and four degrees*. 
[To be continued.} 
LIII. On 
* The passage from the Cape Verd Islands to Cape Verd and the Gambia, 
afforded a not less interesting opportunity of observing the difference in the 
hygrometrical state of the atmosphere at sea, and in the vicinity of the 
continent, in the region of the trade winds. We had entered the N.E. 
trade in the latitude of 24° North, nine degrees to the northward of the Cape 
Verd Islands, and did not lose it until the afternoon of the day on which 
we quitted the Gambia, the strength declining on the approach to the 
continent, but the direction continuing unchanged. On the 28th, 29th, 
and 30th of January, in navigating the first 350 miles of the passage from 
the islands to the continent, the air in the shade and to windward varied at 
different hours of the day from 70°2 to 712, and the dew-point from 63° 
2U2 to 
