EAR 
attraction on the surface has been proved 
by experiments, that substances fall l&i 
feet in one second of time ; and hence that 
if any place within or beyond it may be 
known, as in the former case the force is at 
its distance from the centre, and in the lat- 
ter as the square of its distance from the 
same point. 
The eartli has three motions : that which 
gradually occasions the precession of the 
equinoxes ; that round its axis, which causes 
the succession of day and night, accom- 
plished in 24 hours ; and that of the whole 
mass round tlie sun in a wide orbit, of 
which the luminary of day is the centre ; in 
the latter its axis is constantly parallel to 
itself, and inclined in the same angle to its 
path ; thus producing the visible and per- 
ceptible alteration from spring to summer, 
and from that period to winter. This an- 
nual motion of the earth round the sun is 
performed between the orbits of Venus 
and Mars, with the former and that of Mer- 
cury within its own, or between it and the 
sun in the centre, and those of Mars, Jupi- 
ter, Saturn, &c. above it or without, which 
are called from this cu'cumstance superior 
planets, and the rest inferior. The time 
occupied in performing this revolution is 
365 days, 6 houre, and 49 minutes, or a tro- 
pical year, calculated from an equinox or 
solstice to the same again ; the sidereal year, 
as computed from any fixed star to the 
same point, and seen from the sun, makes 
the revolving of the earth to occupy 365 
days, 6 hours, and 9 minutes : the figure of 
the orbit is elliptical with the sun in one fo- 
cus; the supposed distance is 95 millions of 
miles, admitting the sun’s parallax to be 
8|", or the angle beneath which the semi- 
diameter of the earth would appear- from 
the sun ; “ and the eccentricity of the orbit, 
or distance of the sun in the focus from the 
centre of this elliptic orbit, is about ^th of 
the mean distance.” 
There are nine descriptions of earth, 
which are barytes, strontian, lime, magnesia, 
alumina, yttria, glucina, zireonia, and silica. 
Every substance is an earth which is inso- 
luble in water, or becomes so when com- 
bined with carbonic acid, with little taste 
or scent under the above circumstances, 
and incapable of alteration by fire when in 
a pure state, then capable of being turned 
to white powder, and not exceeding 4.9 in 
specific gravity. 
The word earth is generally applied to 
the whole mass of the globe, and always to 
the mould which supports the growth of 
EAR 
vegetables ; the latter has been attentively 
examined by vai ions cliemists, and found to 
consist of several substances, without any 
regularity in their arrangement. 
EARTHQUAKE. The dreadful conse- 
quences attending sudden and violent 
tremblings of the earth are suflScieut rea- 
sons for attempting to account for their 
causes, but as from the nature of those it 
is utterly impossible to ascertain them accu- 
rately, rational conjecture must be accepted 
in place of actual observation. Every wri- 
ter on the effects of volcanic eruptions con- 
cur in attributing earthquakes to their in- 
ternal operations, which become less fre- 
quent in their neighbourhood after violent 
explosions tlrrough the craters; indeed it 
must be obvious on the first thought, that 
the furious etforts of fire, hot air, and steam, 
exclusive of electric matter cannot but 
produce convulsive motion in the substances 
which confine them, and of more or less 
extent and violence in proportion to the 
cause. When a free passage is obtained, 
the agitation gradually subsides, and is only 
increased at intervals by the escape of 
accumulated matter. Sir AVilliam Hamil- 
ton, who carefully examined all the visible 
phenomena produced by the earthquakes of 
1783, in Calabria, is decidedly of opinion, 
that they originated from under the sea, 
situated between the coast of Calabria and 
the Island of Stromboli, or near the city of 
Oppida, which he illustrates by forming a 
circle round those points, and remarking 
that the most destructive effects were there, 
whence they became gradually less ruinous. 
Mount Stromboli had been unusually quiet 
for some time previous to tliis calamitous 
period, a circumstance highly favourable to 
his conjecture, founded besides on the ex- 
perience of remote ages, when, according 
to Strabo, Campania was subject to fre- 
quent and dreadful earthquakes, which were 
less common and ruinous after Vesuvius 
had become the means of dispersing the 
confined matter. Since that fortunate sera, 
the vicinity of the above mountain has suf- 
fered more from the lava and ashes than 
earthquakes. 
If stronger proofs were necessary, that 
volcanic operations cause this phenomenon, 
the rising of hills near iEtna, or any other 
volcano, and the Lipari Islands, are suffi- 
cient demonstrations how severely the 
eartli must be convulsed by subterraneous 
fires ; those consequences are not, however, 
alwaj^s visible, eartliquakes often occurring 
without any other effect than tlie overturn- 
