374 FROM NEBULA TO NEBULA 



The lunar atmosphere is very possibly considerably more 

 dense than is generally supposed. We know but little about the 

 refractive powers of very rarefied atmospheres when the mean 

 free path of the molecule is of appreciable length. It is not likely 

 however that its density exceeds a few millimeters, and in that 

 case ice when warmed would pass directly into vapor without 

 passing through the liquid form. However tempting the idea 

 might be, and their appearance certainly suggests it, these canals 

 cannot therefore be irrigating channels either natural or arti- 

 ficial. * * * 



In summarizing our observations it cannot be impressed too 

 strongly on the reader that neither the dark fields nor the canals 

 owe their blackness to shadow. Shadows are most conspicuous 

 at lunar sunrise and sunset, and are absolutely invisible at "full 

 moon. These markings are invisible at sunrise and sunset, and 

 are most conspicuous at full moon. Since the outer canals are 

 wholly invisible at sunrise, though the region is well shown, and 

 the inner ones are similarly invisible at sunset, they cannot be 

 due either to troughs or ridges. The blue black color of the 

 fields and canals can only be due therefore to a discoloration of 

 the surface, which develops alike on slopes and levels in fhe 

 lunar summer, and is invisible in the spring and autumn. We 

 know of no mineral which acts in this manner, and the only 

 possible explanation therefore seems to be that it is due to a 

 covering of vegetation. 



Scarcely any professional astronomers look at the moon 

 now-a-days; it is left wholly to amateurs. Many astronomers 

 write text books on astronomy. New editions are constantly be- 

 ing brought out in which they repeat the well worn statement 

 that the "moon is without air, water or vegetation." It is im- 

 possible for a single writer to make headway against such odds. 

 Statements and facts relating to bodies like the moon and Mars, 

 which few astronomers ever look at, make progress but slowly. 

 This is because the text-book astronomers never read them, nor 

 do they believe the observers, if they do. There are too many 

 other things that they must read. * * * 



The writer first began advocating the existence of vegetation 

 on the moon a little over twenty years ago, and has been writing 

 about it ever since. Other astronomers had suggested it before 

 him, but for the last hundred years the matter has been some- 

 what in abeyance, the last prominent astronomer who strongly 

 favored it being Sir William Herschel. The writer hopes that in 

 another twenty years the idea will have gained some currency, 

 but alone, without the help of others, it is hopeless to expect to 

 accomplish much. * * * 



