[ 599 ] 
would be more than fufficient to make them bear the 
weight of the fuper incumbent matter, this compref- 
fion mud be propagated on account of the eladicity of 
the earth, in the fame manner as a pulfe is propa- 
gated through the air ; and again the materials im- 
mediately over the cavity, redoring themfelves be- 
yond their natural bounds, a dilatation will fucceed to 
the comprefiion j and thefe two following each other 
alternately, for fome time, a vibratory motion will be. 
produced at the furface of the earth. If thefe alter- 
nate dilatations and compreffions fhould fucceed one 
another at very fmall intervals, they would excite a. 
like motion in the air, and thereby occafion a con- 
dderable noife. The noife that is ufually obferved- 
to precede or accompany earthquakes, is probably 
owing partly to this caufe, and partly to the grating 
of the parts of the earth together, occadoned by that 
wave-like motion before-mentioned. 
5-7. After the water, that fird came in contact 
with the fire, has formed a cavity, all the red of the 
water contained in the failures, immediately commu- 
nicating with the hollow left by the part that fell in. 
reconciled with each other, but upon this fuppofition. [See Mac- 
laurin’s Fluxions, art. 681, fcfc.] It appears, from fome late and 
accurate obfervations, that the aequatorial parts of the planet Jupiter 
alfo, as well as thofe of the earth, are a little higher than they would 
be, if their rife was owing to the centrifugal force, and he was of. 
uniform denfity ; but if we fuppofe him to be of lefs denfity in the 
aequatorial, than the polar regions, then the form may be fuch as 
he would aflume from the refpedlive gravitation of the feveral parts ; 
and any fluid like our ocean, would not overflow the polar parts, 
(which, upon any other fuppofition, it muft neceflarily do) hut 
would follow his general form, as our ocean does that of the 
earth. 
mud. 
