THE MOON IN MASQUERADE 125 



rays to "ricochet," as it were, and so transmit them to 

 us weakened by repeated reflections. Besides, the 

 sin-shy bottoms materially bring down the average of 

 the general luminosity. 



Whether the moon's atmosphere be extra dense, or 

 especially rare, seems to me to have little bearing on 

 my diagnosis of lunar conditions one way or the other; 

 but my theory may throw some light on the query as to 

 just how rare it is, and why. Undoubtedly the refrac- 

 tion of star rays in occnltations is the surest test we 

 have of a planet's atmospheric density, but in the 

 moon's case due weight has not been given to the cir- 

 cumstance that it is the mountain summits, where the 

 air is thinnest, and not the ball of the planet, that 

 intercepts the light, in this respect furnishing a con- 

 trast to Mars. The chief point, however, is that snow- 

 flakes absorb considerable air in their formation, and 

 when we reflect that practical^}/ the planet's entire 

 (jtiota of irater Is transformed into x//o/r, the impor- 

 tance of this factor on the density of the lunar atmos- 

 sphere may be appreciated. 



The failure of the various scientific tests to dis- 

 cover evidence of any considerable quantity of humid- 

 ity in the moon's atmosphere might lead the precipitate 

 reader erroneously to question the sufficiency of iny 

 theory on that account. Now it is a well known fact 

 that a block of ice placed in a narrow vessel, and ex- 

 posed to a warm atmosphere, will keep its own water 

 of thaw at the freezing point until the last vestige of 

 ice has disappeared. This is practically what takes 

 place on the moon, except that there the water is in- 

 stantly absorbed by the underlying layers of snow, so 

 that a CRYSTALLINE SURFACE is perpetually presented to 

 the sky. Tt is therefore a physical impossibility for 1 

 vapor to rise, save in the lowest spots where the surplus 

 water accumulates in pools and where, also, the snow 



