of the Lower Strata of the Atmosphere. 39 
We shall examine each of the questions in succession. 
1st Question.—How far is the increase of temperature which takes 
place at certain times of the day in proportion as we ascend, in- 
fluenced by the state of the sky and the agitation of the air ? 
It results from my experiments, that the degree of this in- 
crease appears subject, as had previously been observed, to 
the influence of both the circumstances in question. In ge- 
neral, the clearer and more tranquil the weather, and the less 
aqueous vapour there is suspended in the air, the more con- 
siderable is the difference of temperature as we ascend. It 
appeared to me to vary during the finest season of the year 
from 2 to 3 degrees; I never saw it exceed 4 degrees in sum- 
mer and autumn, however clear the weather might be, and 
however favourable the other meteorological circumstances of 
a nature likely to have an influence on this phenomenon. If, 
in this respect, the differences which I observed during the 
summer are inferior to those mentioned by Six, I differ still 
more from that natural philosopher in this, that while he limits 
the increase of the temperature, ascending, to the case of a 
calm and clear sky, it appeared to me to take place constantly, 
at least during the finest season of the year and at the time 
of sunset, and however cloudy the weather might be, provided 
there was not a strong wind. From nearly a hundred obser- 
vations, taken at the times and in the circumstances already 
mentioned, I never failed to remark some increase in the 
temperature upwards, except in the case of a strong wind. 
This augmentation, it is true, was often limited to a few hun- 
dred parts of a degree, and manifested itself in the very low- 
est strata of the atmosphere, ceasing sometimes at the height 
of 40 and even 30 feet.* I have even remarked, on more than 
one occasion, a complete equality among the different ther- 
mometers two or three hours after sunset. This took place, 
Meee ON ES es 
%* On the first of September, at seven o’clock in the evening, in cloudy 
weather, the wind south-west, and pretty strong, the thermometer at 5 feet 
above the ground stood at 12°.7, and at 40 feet, at 12°5. From 40 feet up to 
108 the thermometer underwent no sensible variation. The same thing 
took place in the observations of the 6th September and 4th October, made 
at the game hour. 
