i88 3 .j 
Relations between Earth and Moon . 
455 
i _ _i__ _ _i . 
2*63 3‘°5 4° ’ 
and— 
— = — — — — as before. 
40 24*16 59*56 
The attraction of the earth on the moon varies in conse- 
quence of this excentricity, according to observation, from 
1-3364 to 1*3844 of the attraction or gravity exercised by 
the earth at her own surface. The mean being 1-3604, we 
have— 
_jl_ + 
3604 3604x59*56 
of itself (1-59*56 being the excentricity of the terrestrian lunar 
orbit, and — 
the twofold terrestrian excentricity) equal 1-3546. But in 
“ On some Properties of the Earth ” I have shown, in more 
than one way, that the ocean is the 1-3546 of the mass of 
the earth, and so forth, — certainly a remarkable string of 
coincidences. 
The distance of the moon from the earth is 60*2965 radii, 
or 30*14 diameters of the latter. The uncertainty in this 
distance is held to be — 
60*2965 radii - 59*56 radii =* 0*7365 ; 
which difference is the 1-81 of the former and the 1-80 of 
the latter figure, the mass of the moon being i-8i of that of 
the earth. The difference, — 
_i_ _ _i __ 1 
80 81 6480’ 
is equal to the decrease of solar attraction through the 
length of the diameter of the earth. 
The surface of the moon is to that of the earth as the 
sideral month to the year, or a revolution of the moon round 
the earth to one round the sun. The density of the moon 
is therefore V2*83 of that of the earth. 
