80 On the supposed Tides in the 
“If the earth were wholly fluid, and the same part of its 
surface were always turned towards the moon, the pole of 
the spheroid being immediately under the moon, the lunar 
tide would remain stationary, the greatest elevation being at 
€ points nearest to the moon and furthest from her, and 
the greatest depression in the circle equally distant from 
these points; the elevation being, however, on account of 
the smaller surface to which it is confined, twice as great as 
the depression. The actual height of this elevation, would 
probably be about forty inches, and the depression twenty, 
i ether a tide of five feet. If also the waters were 
c le of assuming, instantly, such a form as the equilibri- 
um would require, the summit of a spheroid equally elevated 
would still be directed towards the moon, notwithstanding 
the earth’s rotation. This may be called the primitive tide 
of the ocean: but on account of the perpetual change of 
place, which is required for the accommodation of the sur- 
ace, to a similar position with respect to the moon, as the 
earth revolves, the form must be materially different, from 
that of such aspheroid of equilibrium. The force employed, 
in producing this accommodation, may be estimated, by con- 
sidering the actual surface of the sea, as that of a wave, 
moving on the spheroid of equilibrium, and producing in the 
water, a sufficient velocity, to preserve the actual form. We 
may deduce, from this mode of considering the subject, a 
theory of the tides, which appears to be more simple and 
satisfactory, than any which has yet been published: and by 
comparing the tides of narrow seas and lakes, with the mo- 
tions of pendulums, suspended on vibrating centres, we may 
extend the theory to all possible cases.” 
“If the centre of a pendulum be made to vibrate, the vi- 
brations of the pendulum itself, when they have arrived at a 
state of permanence, will be per in the same time 
with those of the centre; but the motion of the pendulum 
will be either in the same direction with that of the centre, 
or in a contrary direction, accordingly as the time of this for- 
