-made in the Coquille by M. Duperrey. 287 
tors. Meteorological observations are not less. adapted to ac- 
celerate the progress of this important branch of the nau- 
tical art, than the method generally employed by mariners, 
and which consists in comparing latitudes and longitudes as- 
tronomically determined, with the corresponding latitudes and 
longitudes deduced from the observation of the compass and 
the log. 
The waters of a certain region, when they are transported 
by a current into a region more or less approaching to the 
equator, lose in the passage only a part of their former tem- 
perature. The ocean is thus furrowed by a great number of 
streams of warm and cold water, whose existence the thermo- 
meter manifests, and points out in a certain degree their direc- 
tion. Every one knows the researches of Franklin, of Blag- 
den, of Williams, and of Humboldt, on the equinoctial current, 
which, after being turned back in the Gulf of Mexico, after 
having issued out through the strait of Bahama, moves from 
the south to the north, at a certain distance from the eastern 
coast of America, and proceeds, under the name of the Gulf- 
Stream, to temper the climate of Ireland, of the Shetland 
Isles, and of Norway. At the other extremity of this vast con- 
tinent, along the coasts of Chili and of Peru, a rapid current 
from south to north carries on the other hand as far as Callao 
the cold waters of Cape Horn and of the Straits of Magellan. 
The anomalous temperature of the ocean, in the port of Lima, 
was remarked as far back as the sixteenth century. Acosta, 
indeed, says (lib. ii. cap. 2. pag. 70), that liquors may be 
cooled at Calloa by plunging them in the sea water; but it was 
M. de Humboldt who first proved, by exact experiments, that 
this accidental temperature is the effect, in a great degree at 
least, of a southern current, whose limit is Cape. Blanc: more 
to the north, in the Gulf of Guayaquil, he found no traces of it. 
The numerous observations collected in the Coquille, either 
during its navigation along the coasts of Chili and Peru, or 
during its stay at Conception, at Lima, and at Payta, will fur- 
nish important data relative to this curious phenomenon. At 
Payta, for example, the temperature of the air was in general 
5, 6, ‘and even sometimes 7° Cent. above that of the sea. 
The mean difference of these temperatures, determined by 
thirteen days observations in the month of March, rises to 
5°: during the stay at Callao, a difference was also found in 
the same direction; but it is less than at Payta, which perhaps 
would not have been expected. The journals kept in all the 
other ports, that of Conception in Chili excepted, do not pre- 
sent any thing similar: the water and the atmosphere on an 
average 
