EARTH. 
V.itch is 12 Rhinland feet, amounting to 19 
Dutch miles, and so the whole periphery 
(5840 miles; a mile being, according to him, 
1500 perches, or 18000 Rhinland feet. 
The next that undertook this measurement, 
was Richard Norwood, who, in the year 1635, 
by measuring the distance from London to 
York with a chain, and taking the sun’s meri- 
dian altitude, June 11th, old style, with a 
sextant of about 5 feet radius, found a degree 
■contained 367200 feet, or 69 miles and a half 
and 14 poles ; and thence the circumference 
of a great circle of the earth is a little more 
than 25036 miles, and the diameter a iitfle 
more than 7966 miles. See the particulars 
of this measurement in his Seaman’s Practice. 
The measurement of the earth by Snell, 
though very ingenious and troublesome, and 
much more accurate than any of the ancients’, 
being still thought, by some French ma- 
thematicians, liable to certain small errors, 
the inquiry was renewed, after Snell’s man- 
ner, by Picard and other mathematicians, by 
the king’s command, using a quadrant of 31. 
French feet radius ; bv which they found a 
degree contained 542360 French feet. 
M. Cassini the younger, in the year 1700, 
by the king’s command also, renewed the ex- 
periment with a quadrant of 10 feet radius, 
for taking the latitude, and another of 
feet for taking the angles of the triangles ; 
and found a degree, from his calculation, 
contained 27292 toises, or almost 69-£ English 
miles. 
From the mean of a great many measure- 
ments, the following dimensions may be taken 
as near the truth : 
the circumference 25000 miles, 
the diameter 79574- miles, 
the superficies 198944206 square miles 
the solidity 263930000000 cubic miles, 
Aiso, the seas and unknown parts of the earth, 
by a measurement of the best maps, contain 
160522026 square miles: the inhabited parts 
38922 1 80 ; of which Europe contains 4456065 ; 
Asia, 10768823 ; Africa, 9654807 ; and Ame- 
rica, 14110874. 
Earth, Structure of. After the pre- 
ceding survey of the form and magnitude of 
this globe of earth, the next object of atten- 
tion is the general arrangement of those sub- 
stances of which it is composed. These are 
neither disposed in a regular series, accord- 
ing to their specific gravities, nor yet thrown 
together in total disorder, as if by accident or 
chance. Human industry has hitherto been 
able to penetrate but a very little way into 
the bowels of the earth, and we can but know 
little of its interior parts. The depth of the 
earth, from the surface to the centre, is nearly 
four thousand miles; and yet the deepest 
mine in Europe, that at Cot'teberg, in Hun- 
gary, is hot more than one thousand yards 
deep ; “ the greatest depth, therefore,” says 
an excellent writer, “ to which avarice has 
ever yet penetrated, may be compared to the 
puncture made in the body of an elephant by 
the proboscis of a gnat.” 
From what has been discovered, however, 
of those parts which lie most contiguous to 
our observation, naturalists have compared 
the structure of the earth to the leaves of a 
book, or the coats of an onion. Except, 
indeed, in some of those immense mountains, 
which have existed from the creation, or at 
least from the deluge, where the matter, from 
whatever cause, is more homogeneous, (he 
earth is found to consist of various strata, or 
layers, which differ according to the circum- 
stances of climate and situation. The sur- 
face, in general, evidently consists of a con- 
fused mixture of decayed animal and vege- 
table substances and earths rudely united 
together ; but when we have penetrated below 
the surface, we find the materials bf the globe 
arranged in a more regular manner. Some- 
times, indeed, we find heaps of stone, which 
do not consist of layers, but are confused 
masses of unequal thickness, and are called 
rocks. The strata are, in general, extended 
through a whole country, and perhaps, with 
some interruptions and varieties, through the 
globe itself. These extensive bodies are 
found most regular when the country is fiat, 
being, in that case, nearly parallel to the 
horizon, thpugh frequently dipping down- 
wards in a certain angle ; in many places the 
beds have a wave, as where the country con- 
sists of gently waving hills and vales; here, 
too, they generally dip. In travelling a mile 
we, perhaps, pass through ground composed 
mostly of sand ; in another mile we find it, 
perhaps, composed of clay ; and this is oc- 
casioned by the edges of the different strata 
lying with an obliquity to the horizon. By 
the same kind of projection, mountains, or 
ridges of mountains, are produced, which, in 
general, have what is called a back and a 
face, the former smoother, and the latter 
more rugged. We generally find, too, on 
one side of a mountain, a more gradual ascent 
than on the other ; which is occasioned by the 
strata, which have risen above the general 
level of the country, being abruptly broken 
off 
Dr. Woodward has considered the circum- 
stances of these strata with great attention, 
viz. their order, number, situation with re- 
spect to the horizon, depth, intersections, 
fissures, colour, consistence, &c. He ascribes 
the origin and formation of them a 1 !, to the 
great flood or cataclysmus. At that terrible 
revolution he supposes that all sorts ot ter- 
restrial bodies had been dissolved and mixed 
with the waters, forming altogether a chaos 
or confused mass. This mass of terrestrial 
particles, intermixed with water, he supposes, 
was at length precipitated to the bottom ; and 
that generally according to the order of gra- 
vity, the heaviest sinking first, and the lightest 
afterwards. By such means were the strata 
formed of which the earth consists ; which, at- 
taining their solidity and hardness by degrees, 
have continued distinct ever since. These 
sediments, he farther concludes, were at first 
all parallel and concentrical ; and the surface 
of the earth formed of them, perfectly smooth 
and regular; but that, in course of time, 
divers changes happening, from earthquakes, 
volcanos, See. the order and regularity of the 
strata were disturbed and broken, and the sur- 
face of the earth, by such means, brought to 
the irregular form in which it now appears. 
M. De Buffon surmises that the earth, and 
the other planets, are also parts struck off 
from the body of the sun by the collision of 
comets ; and that, when the earth assumed 
its form, it was in a state of liquefaction by 
fire. But that could not be the method of 
producing the planets ; for if they were struck 
off from the body of the sun, they would 
m’ove in orbits that would pass through the 
4 D 2 
579 
sun, instead of having the sun for their focus, 
or centre, as they are now found ; so that 
having been struck off, they would fall down 
into the sun again, terminating their career, 
as it were, after one revolution only. See 
Geology. 
Earth, its quantity of matter, density, 
and attractive power. Although the relative 
densities of the earth and most of the other 
planets have been known a considerable time, 
it is hut very lately that wx* have come to the 
knowledge of the absolute gravity or density 
of the whole mass of the earth. This has 
been calculated and deduced from the ob- 
servations made by Dr. Maskelype, at the 
mountain Schehallien, in the years 1774, 5, 
and 6. The attraction of that mountain on a 
plummet, was observed ou both sides of it, 
and its mass computed from a number of 
sections in all directions, and consisting of 
stone ; these data being then compared with 
the known attraction and magnitude of the 
earth, gave, by proportion, its mean density, 
which is to that of water as 9 to 2, and to 
common stone as 9 to 5 : from which very 
considerable mean density, it may be pre- 
sumed that the internal parts contain some 
great quantities of metals. 
From the density now found, its quantity 
of matter becomes known, being equal to the 
product of its density by its magnitude. 
From various experiments, too, we know that 
its attractive force, at the surface, is such, 
that bodies fall there through a space of 16^- 
feet in the first second of time : whence the 
force at any other place, either within or 
without it, becomes known; for the -force at 
any part within it, is directly as its distance 
from the centre ; but the force of any part 
without it, reciprocally as the square of its 
distance from the centre. 
Earth, Motion of the. It is now ge- 
nerally granted that, besides the small motion 
of the earth which causes the precession of 
the equinoxes, the earth has two great and 
independant motions ; viz. the one by which 
,t turns round its own axis; in the space of 24 
hours nearly, and causing the continual suc- 
cession of day and night ; and the other, an 
absolute motion of its whole mass in a large 
orbit about the sun, having that luminary for 
its centre, in such manner that its axis keeps 
always parallel to itself, inclined in the same 
angle to its path, and, by that means, causing 
the vicissitudes of seasons; spring, summer, 
autumn, winter. 
It is, indeed, true, that, as to ,sense, the 
earth appears, to be fixed in the centre, with 
the sun and stars moving round it every 
day ; and such, doubtless, would be consi- 
dered as the true nature of the motions in 
the rude ages of mankind, as they are still 
by the rude and unlearned. But, to a think- 
ing and learned mind, the contrary will soon 
appear." 
Bv the diurnal rotation of the earth on its 
axis," the same phenomena will take place as 
if it had no such motion, and as if the sun and 
stars moved round it. For, turning round 
from west to east, causes the sun and all the 
visible heavens to seem to move the contrary 
w’ay, or from east to west, as we daily see 
them do. So, when in its rotation it has 
brought the sun or a star to appear just in the 
horizon in the east, they are then said to be 
rising ; and as the earth continues to revolve 
