THE LUNAR SEAS. 
491 
have the effect of slightly helping to keep them there, certainly not to transfer them 
to this side ; and this not because of the intensity of the earth's attraction on the 
moon, but because of the difference in this intensity as exerted at her centre and at 
the surface remote from us ; such difference enabling the earth to pull her satellite 
slightly away from the water on the remote surface. 
But to proceed. Supposing it to be a fact that " we cannot say there is not a 
residual balance in favour of approach" (of the moon to the earth). Is it not 
making an unusually bold use of inability to infer from it that there is such a 
balance ? But waiving this point also, and assuming, for the sake of applying a 
test to the sjieculation, that the moon "has once been farther off — very much 
farther off," it by no means necessarily follows that she has ever yet come "suffici- 
ently within the influence of the earth's attraction" for " the waters of the moon 
to be transported to our globe." According to the hypothesis, the moon is at 
present neaz-er to the earth than at any former period, and, therefore, nearer than 
at the time of the deluge of the ^'speculation." Now thei-e can be no great diffi- 
culty in determining whether the thing could happen at the present distance ; that 
is, whether the earth's attraction on a body on the moon's surface, placed in the 
straight line joining the centres of the two globes (the most favourable position for 
the success of our world in the struggle), would be greater or less than the moon's 
attraction on the same body. In short. Is the earth's power, at present, to steal a 
" Lunar Sea " greater or less than the moon's power to keep it ? If less now, then, 
a fortiori, according to the hypothesis, it must have been less in all former 
periods. 
Let E be the earth and M the moon, a b the line joining their centres a and b, 
and c a body on the moon's surface in the line A B. Now the attraction of a body 
varies directly as its mass and inversely as the square of its distance from the body 
it attracts ; such distance being measured from centre to centre. 
Putting the earth's radius = 1, the distance of the centres is 60 '2734, and the 
radius of the moon "2729 ; hence the distance of the body c from the seat of the 
moon's attraction is, on this scale, = '2729, and from the centre of the earth 
= 60-2734 — -2729 = 60-0005. 
Also, taking the mass of the earth as unity, that of the moon is -011364. 
Then, if a and A' represent, respectively, the attraction of the earth and moon on 
the body c, we have 
A : a' = 1 X -27292 : -011364 x 6O-OOO52 
= -0744744 : 40-89375 
= 1 : 549-12. 
That is, in round numbers, the earth attracts the body 550 times less than the 
moon does ; or whatever inclination our attractive influence may give a " Lunar 
Sea" to precipitate itself on us, the moon gives it 550 times greater inclination to 
stay at home ; and according to the hypothesis, this disparity of inclination was still 
greater in earlier times, and the more so in proportion to the antiquity of the 
time. 
But suppose the organ of Stay-at-home-ness — I think the phrenologists call it 
" Inhabitiveness" — to be so feebly developed in a ''Lunar Sea," that it ivould pro- 
ceed on its travels, is it certain that it would go to the earth ? Why not to the sun '( 
We are told (page 414) that " it is not likely." So I think. But let us see whether 
the earth or sun would hold out the greatest attractions at present for a " Lunar 
Sea" on its travels. It is simply the question, which of the two bodies atti-acts the 
moon most powerfully ? 
