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ceive upon it the concentrated rays of the moon. Yet no sensible effect was 

 produced upon the thermometer. We must therefore conclude that the light of 

 the moon does not possess the calorific property in any sensible degree. 



This result will create less surprise when the comparative density of sun- 

 light and moonlight are considered. It may be assumed without sensible er- 

 ror that the intensity of the sun's light on the surface of the moon and on the 

 earth is the same, it follows from this, that supposing no light whatever to be 

 absorbed by the moon, but the entire light of the sun to be reflected from its 

 surface undiminished, the intensity of moonlight at the earth would bear to the 

 intensity of sunlight the same proportion as the magnitude of the moon bears 

 to the magnitude of the entire firmament, that is, the proportion very nearly of one 

 to three hundred thousand ; but there is no reflecting surface however perfect 

 which does not absorb the light incident upon it in a very considerable degree, 

 and the rugged surface of the moon must be a most imperfect reflector. It may 

 then be considered as demonstrated that the intensity of moonlight is much more 

 than three hundred thousand times more feeble than that of sunlight. We 

 shall not, then, be surprised at the absence of its heating power. 



But if the rays of the moon be not warm, the vulgar impression that they 

 are cold is equally erroneous. We have seen that they produce no effect either 

 way on the thermometer. 



DOES WATER EXIST ON THE MOON ? 



We shall presently see that telescopic observation proves the non-existence 

 of oceans, seas, or any other large reservoirs of water, on the surface of our 

 satellite. This is not sufficient, however, to establish the total absence of wa- 

 ter upon it, for besides its possible existence in the form of rivers and small 

 lakes too minute to be discovered by the telescope, it might exist in the pores 

 of organized and unorganized matter. 



If, however, water, or any other liquid, existed upon the moon, it \vould be 

 subject to the common process of evaporation, which would take place the 

 more freely because of the absence of an atmosphere. It is evident, then, that 

 the existence of liquids on the moon would necessarily be attended with the 

 existence of an atmosphere surrounding the moon composed of the vapor 

 of those liquids. It is difficult to imagine how such an atmosphere could ex- 

 ist without clouds, but its non-existence is conclusively proved by the fact that 

 its presence cannot be detected by the optical test above-mentioned, by which 

 the absence of an atmosphere is proved an atmosphere of vapor, having in > 

 common with air and other transparent media the property of refraction, its ef- ? 

 feet on the stars will be similar, and consequently the same test which proves l 

 the absence of an atmosphere of air equally proves the absence of an atmo- < 

 sphere of vapor. 



