at the times of the
southing and northing of the moon, and that in a greater degree when this
coincides with the southing and northing of the sun, and this in a still
greater degree about the times of the equinoxes. This decrease of the
gravity of all bodies during the time the moon passes our zenith or nadir
might possibly be shewn by the slower vibrations of a pendulum, compared
with a spring clock, or with astronomical observation. Since a pendulum of
a certain length moves slower at the line than near the poles, because the
gravity being diminished and the vis inertiae continuing the same, the
motive power is less, but the resistance to be overcome continues the same.
The combined powers of the lunar and solar attraction is estimated by Sir
Isaac Newton not to exceed one 7,868,850th part of the power of
gravitation, which seems indeed but a small circumstance to produce any
considerable effect on the weight of sublunary bodies, and yet this is
sufficient to raise the tides at the equator above ten feet high; and if it
be considered, what small impulses of other bodies produce their effects on
the organs of sense adapted to the perception of them, as of vibration on
the auditory nerves, we shall cease to to be surprised, that so minute a
diminution in the gravity of the particles of blood should so far affect
their chemical changes, or their stimulating quality, as, joined with other
causes, sometimes to produce the beginnings of diseases.

Add to this, that if the lunar influence produces a very small degree of
quiescence at first, and if that recurs at certain periods even with less
power to produce quiescence than at first, yet the quiescence will daily
increase by the acquired habit acting at the same time, till at length so
great a degree of quiescence is induced as to produce phrensy, canine
madness, epilepsy, hysteric pains or cold fits of fever, instances of many
of which are to be found in Dr. Mead's work on this subject. The solar
influence also appears daily in several diseases; but as darkness, silence,
sleep, and our periodical meals mark the parts of the solar circle of
actions, it is sometimes dubious to which of these the periodical returns
of these diseases are to be ascribed.

As far as I have been able to observe, the periods of inflammatory diseases
observe the solar day; as the gout and rheumatism have their greatest
quiescence about noon and midnight, and their exacerbations some hours
after; a