86 IN STARRY REALMS. 



water from the moon or not, the fact of that absence cannot 

 be questioned. The moon has been subjected to careful 

 scrutiny for centuries, yet no one has ever seen any 

 genuine ocean or sea, no one has ever seen any indication 

 of the present existence of water, and we are entitled to 

 assert that water, in a liquid form, is absent from the 

 surface of our satellite. 



On the allied question as to the existence of air around 

 the moon something must now be said, and here let us 

 understand distinctly the problem which awaits solution. 

 I do not here enter on the vexed question as to the nature 

 of the boundary which separates the higher limits of our 

 atmosphere from the emptiness of space ; it is quite suffi- 

 cient for our present purpose to remark that the great 

 mass of the encompassing air lies within a few miles of 

 the earth's surface, though no doubt the more attenuated 

 portions extend with ever-declining density to a distance 

 above the surface which appears at present indeterminate. 

 It is, however, certainly known that an atmosphere is 

 found in the vicinity of many of the other globes in the 

 universe besides our earth, though there is the widest 

 difference both in its density and extent, as well as in its 

 material composition. The sun, for instance, is encom- 

 passed by a stupendous atmosphere comparable in depth 

 and density with his tremendous mass. Similarly the 

 other planets have gaseous envelopes. There is Mars, 

 the world that seems most like our own in other re- 

 spects, and it too is encompassed with an atmosphere of 

 some sort, though we have no reason to think it re- 

 sembles in any degree the atmosphere which is suitable 

 for our respiration. Nor are Venus and Jupiter void of 



