Temperature of the Terrestrial Globe. 11 
upon this planet is evidently insensible. The temperature of the 
surface differs therefore, very little from that of planetary spaces, or 
from that which is observed at the poles of our globe. e have 
made known this last result in a discourse recently delivered before 
the Academy. It is evident we can apply it only to the most dis- 
tant planets. We know of no means of assigning with any precision 
the mean temperature of the other planetary bodies. ‘The motion 
of the air and waters, the extent of the seas, the elevation and form 
of the surface, the effects of human industry and all the accidental 
changes of the earth’s surface, modify the temperatures of each cli- 
mate. The character of phenomena attributable to general causes 
exists: but the thermometrical effects observed at the surface are 
different from what they would be without the influence of accessory 
causes. 
The motion of the waters and of the air, tends to modify the ef- 
fects of heat and cold. 
It renders their distribution more uniform, but it would be impos- 
sible for the atmosphere to supply the place of that universal cause 
which supports the common temperature of the planetary spaces ; 
and if this cause did not exist, we should observe, notwithstanding 
the atmosphere and seas, an enormous difference between the tem- 
peratures of the equatorial and polar regions. 
It is difficult to know how far the atmosphere jatlayuncs the mean 
temperature of the globe; and in this examination we are no longer 
guided by a regular mathematical theory. It is to the celebrated 
traveller, M. de Saussure, that we are indebted for a capital — 
ment, which appears to throw some light on this question. 
The experiment consists in exposing to the rays of | the-sun,-2 a 
vessel covered with one ‘or more plates of glass, very transparent, 
and placed at some distance one above the other. ‘The interior of 
the vessel is furnished with a thick covering of black cork, proper 
for receiving and preserving heat. The heated air is contained in 
all parts, both in the interior of the vessel and in the spaces between 
the plates. Thermometers placed in the vessel itself and in the 
intervals above, mark the degree of heat in each space. This in- 
strument was placed in the sun about noon, and the thermometer in 
the vessel was seen to rise to 70°, 80°, 100°, 110°, (Reaumur,) 
and upwards. The thermometers placed in the intervals between 
the glass plates indicated much lower degrees of heat, and the heat 
decreased from the bottom of the vessel to the highest interval, 
