[rood] 
the heavy er lubfide. As when Water, Beer, or other 
thin fluids, be gradually heated by a fire underneath i 
the lower parts, being tiril warmed, afcending to the 
top, while the colder and heavyer lubfidey whence we 
find, in fuch cafes that Bubbles do arife, and that at the 
top is warmer then that at the bottom. But in cafe what 
is warmed, be of a thicker confiftence, lo as that the 
parts cannot readily (hift places, that at the bottom will 
be hotter ; and in cafe it be heated by fire over it, there 
will ( I fuppofe J be not fuch bubbliitg (or not fo much of 
it,) that at the top being firit heated. 
From Inch confideration as this, Dr. G^r^^/z doth well 
obferve, that fome parts of the ^/r being thus (hy rare- 
fadlion, or increafing the fpring thereof, or otherwife,) 
become lighter then others; thefe heavyer parts, rufhing 
into the places of thofe lighter, may caufe a wind as from 
inch parts; (in like manner as, on a like occafion, a Tyde 
or Current would arife in water; ) and other accidents 
ofa like nature. And contrarywife, on a contrary oG- 
cajion. 
And this I take to be very true, (though fuch accidents 
happening very variouQy and uncertainly, will caufe 
luch confufion of motions, and difturbance of each o- 
ther, that it will be hard to reduce them to a regular ad- 
juftment.) 
But I add thereunto, that the Earths diurnal motion, 
compounded with its annual, (ii we admit that hypo- 
thefis, as moft do now a- days J the one in fome parts ac- 
celerating, in others retarding theother; and its diffe- 
rence in different times of the year, (by reafon of the 
obliquity of the ^dtackjio the EquinoHial,) and in diffe- 
rent times of the month (becaufe of the Moons different 
pofition, which is an Appendance to the Earths motion, 
anddoththereby differently affed it,) and according to 
the different place of the Earth and Moon, as to the A- 
phelion or Perihelion of the one, and the Apogseum or 
Perigseum 
