other parts of the globe, as to render any at- 
tempt at a general theory vain. 
From the vast expanse of oceanic waters, 
arises in the antieut hemisphere, that wide 
continent, which contains Asia, Europe, and 
Africa; and in the modern hemisphere the 
continent of America, which forms a kind 
or eparate island, divided bv a strait of the 
sea from the antient continent. In the 
latt. r many discoveries of great importan e 
to gt ography, are of very modern date, and 
it is not above 60 years since we obtained an 
imperfect idea of,the extent of Siberia and the 
Russian empire, nor above 25 since ample, 
real, and accurate knowledge of these wide 
regions began to be diffused, bo that, in 
truth, America may besai 1 to have been dis- 
covered before Asia; and of Africa our know- 
ledge continues imperfect, while the latest 
observations, instead of diminishing, rather 
increase our idea of its extent. 
But the grandest division of the antient 
continent is Asia, the parent of nations, and 
of civilization : on tiie north-east and south, 
surrounded by the ocean; but on the west, 
divided by an ideal line from Africa: and 
from Europe by boundaries not very strongly 
impressed by the hand of nature. The Rus- 
sian and the Eut'kish -empires, extending over 
large portions of both continents, intimately 
connect Asia with Europe. But for the sake 
of clearness and precision, geographers retain 
the strict division of the antient continent 
into three parts, which, it not strictly natural, 
is ethical, as tne manners of the Asiatic sub- 
jects of Russia, and even of Turkey, differ 
considerably from those of the European in- 
habitants ot those empires. 
A description of tire four quarters of the 
globe, and of the several kingdoms and states 
into wh cli they are divided, belongs rather 
to a work devoted exclusively to geography, 
than to a dictionary of arts and sciences: we 
shad therefore forbear entering more into 
detail in this article. 
GEOLOGY, a science which treats of 
the decomposition and changes to which the 
stony part of our globe has been subjected. 
If it was permitted to man to follow, du- 
ring several ages, the various changes which 
are produced on the surface of our globe bv 
the numerous agents that alter it, we should 
at this time have been in possession of the 
most valuable information respecting these 
great phenomena: but thrown as we are, al- 
most by accident, upon a small point of this 
vast dieatre of observation, we fix our atten- 
tion for a moment upon operations which 
have been the work of nature for ages; 
and we are unable either to perceive or to 
foretel the results, because several ages are 
scarcely sufficient to render the effects or 
changes perceptible. 
It must be allowed that those men who, by 
the mere efforts of their imagination, have en- 
deavoured to form ideas respecting the con- 
struction, and the great phenomena, of this 
globe, have numerous titles to our indul- 
gence. In their proceedings we behold the 
efforts of genius, tormented with the desire 
of acquiring knowledge, and irritated at the 
prospect of the scanty means which nature 
has put in its power ; and when these natu- 
ralists, such as M. de Buffon, have possessed 
the power of embellishing their hypotheses 
with every ornament which imagination and 
eloquence can furnish, either as instruments 
GEOLOGY. 
of illusion or entertainment, we ought to con- 
sider ourselves indebted to them. 
For our part, we shall confine ourselves to 
a few ideas respecting the successive decom- 
positions of our planet, and shall endeavour 
to avoid every departure from observation 
and matter of fact. 
The slightest observation shews us that 
living beings are kept up and perpetuated 
only by successive decompositions and com- 
binations. A slight view of the mineral king- 
dom exhibits the same changes ; and out- 
globe, in alt its productions, presents conti- 
nual modifications, and- a circle of activity, 
which might appear incompatible with the 
apparent inertia of earthy products. 
In order to arrange our ideas with greater 
regulant , we mav consider this globe in two 
different states. We shall first examine the 
primitive rock which forms the nodule or 
central part. This appears to contain no 
germ of life ; includes no remains or part of 
any living being ; and from every circum- 
stance appears to have been of primitive for- 
mation, anterior to the creation of animated 
or vegetating bodies. We shall pursue the 
various changes which are daily produced bv 
the destructive action of such agents as alter 
or modi- y this substance. 
We shall then proceed to examine what 
stones have been successively placed upon 
this, and what are the decompositions to 
which these secondary rocks have been sub- 
jected. 
1. The observations of naturalists all unite 
to prove that the primitive part of the globe 
consists of the stone known by the name of 
granite. The profound excavations which 
tiie art of man, or currents of water, have 
made in the surface of our planet, have all 
uncovered this rock, and have been incapa- 
ble of penetrating lower : we may therefore 
consider this substance as the nucleus of the 
globe ; and upon this substance it is that all 
matters of posterior formation rest. 
Granite exhibits many varieties in its form, 
composition, and disposition : but it in gene- 
ral consists of an assemblage of certain silice- 
ous stones, such as quartz, schorl, feldtspar, 
mica, &c. ; and the more or less consider- 
able magnitude of these elements of granite, 
has caused it to be divided into coarse-grain- 
ed granite, and fine-grained granite. 
It is thought that these rocks owe their ar- 
rangement to water ; and if we may be per- 
mitted to recur, by an effort of the imagina? 
lion, to that epoclia in which, according to 
sacred and profane historians, the water and 
earth were confounded, and the confused 
mixture of ail principles formed a chaos, we 
shall see that the laws of gravity inherent in 
matter must have carried it down, and ne- 
cessarily produced the arrangement which 
observation at present exhibits to us. The 
water, as the least heavy, must have purified 
itself, and arisen to the surface by a filtration 
through the other materials: while the earthy 
principles must have precipitated, and form- 
ed a mud, in which all the elements of stones 
were confounded. In this very natural order 
of things, the general law of affinities, which 
continuity tends to bring together ad analo- 
gous parts, must have exerted itself with its 
whole activity upon the principles of this al- 
most fluid paste ; and the result have been a 
number of bodies of a more definite kind, in 
crystals more or less regular; and from this 
S 37 
muddy substance, in which the principles of 
the stones were confounded that compose the 
granite, a rock must have been produced, 
containing the elementary stones ail in pos- 
session oi their distinct forms and characters. 
In tuis manner it is that we observe salts of 
very different kinds develope themselves in 
waters which hold them in solution; and in 
this manner it still happens that crystals of 
spar and gypsum are formed in clays which 
contain their component jyirts. 
It may easily be conceived that the laws of 
gravitation must have influenced the arrange- 
ment and disposition of the products. The 
most gross and heavy bodies must have fallen, 
and the lightest and most affenuated sub- 
stances must have arranged themselves on 
tiie surface of the foregoing ; and this it is 
which constitutes the primitive schist!, the 
gneis, the rocks of mica, &c. which com- 
monly repose upon masses of coarse-grained 
granite. 
1'he disposition of the fine-grained granite 
in strata or beds, appears to depend on this 
position, and the fineness or tenuity of its 
parts. Being placed in immediate contact 
with water, this fluid must naturally have in- 
fluenced the arrangement which it presents to 
us ; and the elements of this rock being sub- 
jected to the effect of waves, and the action 
of currents, must have formed strata. 
The rocks of granite being once establish- 
ed as the nucleus of oar globe, we may, Irom 
the analysis of its constituent principles, and 
by attending to the action of the various 
agents capable of altering it, follow the 
changes to which it has been subjected, step 
by step. 
Wate. is the principal agent whose effects 
we shall examine. 
This fluid, collected in the cavity of the 
ocean, is c. rried by the atmosphere to the tops 
of the most elevated mountains, where it is 
precipitated in rain, and forms torrents, which 
return with various degrees of rapidity into 
the common reservoir. 
This uninterrupted motion and fall must 
gradually attenuate and w ear away the hard- 
est rocks, and cam their detached parts to 
distances more or less considerable. The 
action of the air, and the varying tempera- 
ture of the atmosphere, facilitate the attenua- 
tion and the destruction of these ro ks. Heat 
acts upon their surface, and renders it more 
accessible and more penetrable to the water, 
which succeeds ; cold divides them, by freez- 
ing. the water which has entered into their 
texture ; the air itself affords the acid prin- 
ciple, which attacks the limestone, and causes 
it to effloresce ; the oxygen unites to the 
iron, and calcines it: insomuch that this con- 
currence of causes favours the disunion of 
principles ; and consequently tire action of 
water, which clears the surface, carries away 
the products of decomposition, and makes 
preparation for a succeeding process of the 
same nature. 
The lirst effect of the rain is there- 
fore to depress the mountains. But the 
stones which compose them must resist in 
proportion to their hardness ; and we ought 
not to be surprised when we observe peaks 
which have braved the destructive action of 
time, and still remain to attest the primitive 
level of the mountains which have disap- 
peared, The primitive rocks, alike inacces- 
sible to the injury of ages as to the animated 
