GEOLOGY. 
lous mineral principles are raised, in a state 
of vapour, through the different clefts of 
the earth, until they arrive near to its sur- 
face, where they enter into various combi- 
nations, the result of this is the produc- 
tion of the numerous mineral substances 
which the earth contains. 
Besides these, who consider an inherent 
or central fire as necessary to the formation 
and continuation of this globe, there are 
others who refer the particular modifica- 
tion of the form of its surface to the opera- 
tion of subterraneous fires, acting partially 
by the incalescence of pyrites and volcanic 
eruptions, with accompanying earthquakes ; 
amongst those who have adopted this opi- 
nion, may be mentioned Steno, Lazare, 
Moro, and Ray. 
To produce the vast effects necessary to 
give form to a planet, or to modify its sur- 
face anew, must of course require the most 
powerful physical agents. In the various 
systems, therefore, which human ingenuity 
has devised, with the hope of pointing out 
the natural means which have been employ- 
ed in these prodigious operations, the pow- 
erful agency of fire or of water has been gene- 
rally referred to ; and hence geologists have 
been rather whimsically named, according 
to the particular agency which they have 
supported in their discussions, Plutonists, 
and Neptunists. The systems already here 
noticed, it is obvious, are those in which 
fire has been adopted, as almost the sole 
agent ; in those which next will engage our 
attention, recourse has been had to the 
combined powers of both agents. 
Dr. Burnet, whose system manifests a 
considerable portion both of ingenuity and 
judgment, supposes the earth to have ori- 
ginally been a fluid mass, the component 
parts of which became arranged according 
to their gravity ; hence the heaviest mat- 
ters were deposited at the centre, and 
above these were disposed, in concentric 
layers, the substances w'hick were less and 
less heavy, and on the surface was the 
earth, covered all round by the water, 
which was itself invested by an unctuous 
matter, around which existed the circum- 
ambient air. By the subsequent intermix- 
ture of the oily matter and earth, and other 
arrangements of its several component 
parts, the crust of earth acquired a smooth 
form, and obtained those qualities which 
were necessary for the existence of orga- 
nized beings. At this period, the axis of 
the globe was supposed to be parallel with 
that of its orbit, the days and the nights to 
be equal in length, and a uniform season to 
have existed, resembling a perpetual spring ; 
but on the crust of the earth drying, from 
the ardency of the heat, it became violently 
rent asunder, falling into, and giving open- 
ings for the vast abyss of waters beneath : 
hence the axis of the globe became in- 
clined, occasioning those changes of the sea- 
sons, and of the length of the days and nights, 
which now exist ; and thus also were pro- 
duced the beds of the ocean, with the valiies 
and the numerous mountainous elevations. 
Mr. Whiston conjectured, that the earth 
was originally a comet, which, at the period 
mentioned in the Mosaic account, as that 
of the creation of the world, had its orbit 
rendered nearly circular, and such an ar- 
rangement formed of its component parts, 
as made it fit for the existence of the vege- 
table and animal creation : having existed 
in this state its allotted time, lie supposes a 
comet to have passed so near to the earth 
as to have involved it in the vapours form- 
ing its tail, and which, being condensed, 
fell in torrents, and produced the deluge 
described by Moses; the action of the c p- 
met on the earth itself, having been suffi- 
cient to produce, at the same time, those 
irregularities of its surface, which form 
chains of mountains and the vast beds of 
the ocean. 
Mr. Pallas having assumed the formation 
of the sea and the primitive rocks, sup- 
posed that, with ^ the sand produced by 
their constant disintegration, the sea must 
have deposited such inflammable and fer- 
ruginous matters, as, being disposed in 
beds on the granite, would form the fuel of 
volcanoes ; these, raising and bursting the 
solid beds under which they had existed, 
and which they must have altered by fusion 
or calcination, would raise up the mountains 
of schist and of lime-stone. The shores of 
the sea being gradually augmented, the sea 
, being diminished and driven back, whilst 
its bed was raised in different parts by the 
power of volcanoes, the formation of the 
mountains containing petrifactions would 
take place. Lastly, he supposed, after the 
earth had been well stocked with vegeta- 
bles and animals, that by some enormous 
eruptions at the bottom of the sea, its wa- 
ters may have been made to inundate the 
whole horizontal surface of the earth, and 
even those mountains which have not ex- 
ceeded one hundred toises in height. 
The system of Dr. Hutton resembles, in 
many points, that which has been just no- 
ticed ; but its several parts are better con- 
