BAPIDITT OF THEIE 4101101?. 
367 
immense number of bolides and falling-stars were perceived; 
arid that those meteors had everywhere the same brilliancy, 
throughout a space of 921,000 square leagues. 
Astronomers who have lately been directing minute atten- 
tion to falling-stars and their parallaxes, consider them as 
meteors belonging to the farthest limits of our atmosphere, 
between the region of the Aurora Borealis and that of the 
lightest clouds.* Some have been seen, which had not more 
than 14,000 toises, or about five leagues of elevation. The 
highest do not appear to exceed thirty leagues. They are 
often more than a hundred feet in diameter : and their swift- 
ness is such, that they dart in a few seconds through a space 
of two leagues. Of some which have been measured, the 
direction was almost perpendicularly upward, or forming an 
angle of 50° with the vertical line. This extremely remark- 
able circumstance has led to the conclusion, that failing-stars 
are not aerolites which, after having hovered a long time in 
space, unite on accidentally entering into our atmosphere, 
and fall towards the earth.f 
Whatever may be the origin of these luminous meteors, it 
is difficult to conceive an instantaneous inflammation taking 
place in a region where there is less air than in the vacuum 
of our air-pumps ; and where (at the height of 25,000 toises) 
the mercury in the barometer would not rise to 0'012 of a 
line. We have ascertained the uniform mixture of atmos- 
pheric air to be about 0 003, only to an elevation of 3000 
toises ; consequently not beyond the last stratum of fleecy 
clouds. It may be admitted that, in the first revolutions 
of the globe, gaseous substances, which yet remain unknown 
to us, have risen towards that region through which the 
falling-stars pass ; but accurate experiments, made upon 
mixtures of gases which have not the same specific gravity, 
show that there is no reason for supposing a superior stratum 
of the atmosphere entirely different from the inferior strata. 
Gaseous substances mingle and penetrate each other on the 
* According to the observations which I made on the ridge of the 
Andes, at an elevation of 2700 toises, on the moulons, or little white 
fieecy clouds, it appeared to me, that their elevation is sometimes not less 
than 6000 toises above the level of the coast. 
t M. Chladni, who at first considered falling-stars to be aflrolites, sub- 
sequently abandoned that idea. 
