286 Report of the Voyage of Discovery 
tor; at the Isle of France, at St. Helena, at Ascension, be- 
tween the tropics ; our navigators had the incredible patience 
to observe the thermometer and the barometer at every quarter 
of an hour, day and night, for whole weeks. So much pains, 
will not be lost; observations so minutely exact, so detailed 
will furnish valuable data on the law which connects cor- 
responding atmospheric temperatures with the different hours 
of the day; on the value of the diurnal and nocturnal baro- 
metric period; on the hours of the maxima and the mi- 
nima, &c. ‘Thanks to the extreme complaisance of M. Del- 
cros, (a very distinguished geographical engineer, ) in going at 
the request of one of us, to ‘loulon,—in order to compare the 
instruments of the Coquille with a barometer which belongs 
to him, and which has agreed for several years with that of the 
Observatory,—we shall be able to decide that which indeed 
is scarcely any longer a question, since the observations of 
MM. Boussingault and Riviero have been received in Europe, 
whether the mean pressure of the atmosphere be the same in 
all climates. bites 
Since the celebrated voyages of Cook, no one any longer 
doubts that the southern hemisphere is in mass decidedly 
colder than the northern;—but at what distance from the 
equinoctial regions does the difference begin to be felt? Ac- 
cording to what law does it become greater in proportion as 
the latitude augments ? When these questions shall have been 
completely resolved, the various causes to which this great 
phzenomenon has been attributed may be submitted to an ex- 
act investigation. Already the stay of M. Duperrey at the 
Malouines, will show that by 51°4 of latitude, the difference 
of climate is very great. We see, in effect, that at the anchor- 
age of the Bate Francaise, from the 19th to the 30th of No- 
vember 1822, the mean temperatures of the atmosphere and 
of the sea were respectively : . Les 
+ 8°°O and + 8° 2 Cent. 
The month following, from the 1st to the 18th, we found : 
+ 10° 0 and + 9° 4, 
We can then adopt + 9°: 0 Cent. for the mean temperature 
of the Malouines, in the thirty days which precede the sum- 
mer solstice of these regions. London is precisely under 
the latitude of Baie Frangaise. Then the mean tempera- 
ture of the twelve last days of May, and of the eighteen 
first days of June, according to the tables published by the 
Royal Society, is about 15° Cent. : that is, 6° more than at the 
Malouines. 
The inquiry respecting the direction and swiftness of cur- 
rents merits in the highest degree the attention of naviga- 
tors. 
of be 
