Distribution of Heat over the Globe. 19 
It appeared to me very important to establish, by obser- 
vations made at every hour, at different periods of the year, 
and under different latitudes, the degree of confidence that can 
be placed in those results which are called Mean Tem'peratures. 
I have selected from the registers of the Royal Observatory at 
Paris clear and calm days, which offered at least ten or twelve 
observations. Under the equator, I have spent whole days in 
determining the horary increments and decrements of tempera- 
ture, in marking the thermometer both in the shade and in the 
sun, and also the progress of evaporation and humidity ; and 
in order to avoid calculation, I measured with a quadrant the 
altitude of the sun at each observation. I chose days and 
nights completely calm, and when the heavens were entirely free 
from clouds, because the mass of vesicular vapours interrupts 
the radiation from the earth. The result of these experiments 
has been very satisfactory, and proves, what had already been 
deduced from the coincidence between the temperature of the 
earth and the mean of daily observations, and from the regular 
progress of the mean temperatures of months in different years, 
that the effects of small disturbing causes may be compensated 
by a great number of observations I have obtained analo- 
gous results by taking, for several months, the mean of 9 o’clock 
in the morning, of sunrise and midnight. I have computed the 
temperatures by the distance of the maximum expressed in time, 
and on the supposition of an arithmetical progression. I have 
found that, under the Torrid Zone, the morning curve from 
sunrise to the maximum^ differs very regularly from the even- 
* On the 3d and 4th September 1811, lat. 48°. 5(y. 
Sum of the temperatures 
True mean temperature, 
taking into account the 
Half sum of the two ex<^ 
during 24 hours. 
duration. 
treme temperatures. 
625°.71 Fahr. 
57°.92 Fahr. 
58°. 28 Fahr.. 
6r2.4g 
59.90 
61.88 
834.67 
66.74 
65.12 
834.67 
66.74 
68.00 
835-37 
66.74 
63.50 
The three last days shew 
63.61 Mean. 63.35 Mean, 
an equality ^of temperature, which is very surprising, 
and which does not appear but in the true naeans. — H. 
