THE LUNAR SEAS. 



493 



Fig. 1. 



Eig. 2. 



face of the globe to be smooth, it would be surrounded by "a stratum of water, B, 

 of equal depth all over, and this again by an atmosphere also of equal depth. 

 As soon, however, as the smooth surface gets broken up and converted into 

 heights and hollows, the water would betake themselves to the lower parts — 

 that is, the parts nearest the centre of 

 gravity — leaving the higher or more dis- 

 tant parts dry, these again covered with 

 an atmosphere now of unequal depth, 

 this varying with the height, that is, the 

 distance from the centre of gravity of the 

 different parts of the surface. This may 

 be said to be almost the condition of our 

 earth, varied by tides in the sea, and winds, 

 &c, in the atmosphere : the cause of these 

 is no subject for discussion here. Let 

 us now suppose a globe (fig. 2) in which 

 the centre of gravity, B, does not coincide 

 with the centre of symmetry, A. Draw a 

 diameter through these points (A and B) 

 and prolong it to C ; the laws of gravita- 

 tion will in this case make all the waters 

 belonging to such a globe concentrate 



about the prolonged diameter on the side of the globe nearest to the centre of 

 gravity, and, provided the surface be altogether smooth, they will form a perfectly 

 circular sea, D, deepest in the centre, gra- 

 dually shallowing towards its circumfe- 

 rence ; this again overlaid by all the atmo- 

 sphere, E, assuming in its outline in like 

 manner a perfectly circular form and also 

 deepest in the centre ; inequalities in the 

 surface of the globe will of course modify 

 these appearances, but a sufficient dis- 

 tance between the centres will occasion 

 that side of the globe most distant from 

 the centre of gravity to be as destitute of 

 water or air is that portion of the moon's 

 surface which has ever been exposed to the 

 investigation of our telescopes. Unite two 

 such globes as in fig. 3. In which A, 

 representing the earth, has its seas distributed all over its surface, the whole 

 having an enveloping atmosphere, and B, the moon, having its centre of gravity, cc, 

 more distant from the earth than its centre of symmetry, B, then its water and air 

 would take the form represented in the figure ; and the moon always keeping the 

 same side towards the earth, it is quite evident that her sea and her atmosphere 

 could never be seen by an inhabitant of the earth. It is thus clear that no moun- 

 tain ridges are required to keep the Lunar Seas from flowing towards the side next 

 our earth, nor in this case would any of the visible inequalities there ever be 

 able to retain the smallest appreciable quantity of either air or water. 



The effect of gravitation, as exerted by the earth on the waters of the moon, 

 supposing it thus constituted, is by no means so readily understood ; but strange 

 as it may seem, it would only occasion such a tide in the Lunar Seas as would tend 

 to increase their central depth ; in other words, to heap up their waters in that 

 part of the moon which lies most distant from the earth. 



Even to the unassisted eye the surface of the moon showing different shades of 

 colour, may suggest the idea of heights and hollows existing in that planet ; the 

 telescope proves the existence of mountain ranges generally of a circular form, and 

 of large comparatively level plains, which at one time were supposed to be seas, 

 and hence their names, "Mare Nubium," &c, &c. Modern observation proves 

 that no waters roll in these seemingly arid wastes — in my opinion, the inquiry 

 which here naturally suggests itself to the observer is not, what has become of the 

 waters of these so-called seas ? but. did waters ever exist in them ? When examined 



