METEORS AND METEORIC STONES. 215 



ray can reach us from probably not the thou- 

 sandth part of the distance. 



But though, in those upper parts of the atmo- 

 sphere, there is the least matter in the same space, 

 we must not on that account suppose that nature 

 is there least active. We have noticed, again and 

 again, that matter is the clog of motion ; and as 

 the most active substances that mingle with the 

 atmosphere have the greatest tendency to ascend 

 in it, we may properly suppose that they occupy 

 the upper parts of it ; and that their motions and 

 oppositions are not only perfectly adequate to the 

 production of all the luminous meteors that appear 

 there, but also of forming out of the scattered 

 materials which float at that airy height, the me- 

 teoric stones of which so many are recorded as 

 having fallen to the ground. 



Lower than that, but still in air so fine that it 

 will float nothing that can be visible to our sight 

 as matter, whatever it may be in appearance as 

 light, there may be a perpetual formation of 

 clouds, not one of which may be able to find its 

 way through the denser and warmer air below. 

 In those high regions of the air, there must indeed 

 be an action of heat in the atmosphere much 

 greater than that which takes place on the earth, 

 otherwise there could not be snow on the summits 

 of the loftiest mountains. On some of those moun- 

 tains there is continual frost, except in the direct 

 rays of the sun, and even a lower temperature 

 than that at which, under ordinary circumstances, 

 water freezes. It is true, that as the whole, or 

 at least the greater part of the sunbeams is reflected 

 back into the atmosphere by the white snow, the 

 air around those lofty summits must be warmer 



