402 J. R. Mayer on Celestial Dynamics. 
other, and then the action of the moon on the earth’s rotation be- 
comes zero. This happens when both hemispheres are arranged 
in a certain manner symmetrically, or when no parts of the 
earth can change their relative position; in the latter case a sort 
of symmetry is produced by the rotation. 
The form of the earth deviates from a perfectly symmetrical 
sphere on account of the three following causes:—(1) the flat- 
he attraction of the sun and the moon disturbs the equilibrium 
of this mass, and two flat mountains of water are formed. The 
top of one of these is directed toward the moon, and the summit 
of the other is turned away from it. A straight line passing 
through the tops of these two mountains is called the major axis 
of this earth-spheroid. : 
In this state the earth may be imagined to be divided into 
three parts—a smaller sphere, and two spherical segments at- 
. elevations of the tidal wave. The attraction of the moon on 
‘| 
the one nearest the moon, is attracted toward the west because 
its mass is principally situated to the east of the moon, and the 
opposite mountain, which is to the west of the moon, is at 
tracted toward the east. The upper tidal elevation is not only 
pposite 
protuberance. ‘The pressure from east to west of the upper ele- 
vation preponderates therefore over the pressure from west 
east of the opposite mountain; according to calculation, these 
quantities stand to each other nearly as 14 to 18. From the re- 
lative position of these two tidal protuberances and the —— 
-sp 1 ' 
toward the centre of gravity of the moon, a pressure results, 
