PHILOSOPHY. 
bodies aft, therefore, on other bodies, at fuch diftances as 
to produce equal momenta in the agent and patient ; con¬ 
fequently, if free to move, or uninfluenced by paramount 
motions, their reciprocal aftions and re-aftions oblige 
them to revolve round a fulcrum or centre of the maffes, 
neceflarily producing equal momenta by forces of impulfe, 
which, diverging through a fphere, are in divers bodies 
to each other inverfely as thefquaresof their diftances. 
7. The motion of maffes round a fulcrum or centre of 
the maffes proves its mechanical origin, and that it is tire 
effeft of equilibrium of momenta, in which, the maffes 
being conftant quantities, the diftances from the centre 
of motion tnuft be inverfely as thofe quantities. 
8. Hence it is that the earth and moon revolve mecha¬ 
nically round the centres of their mafles, at fuch diftances, 
that their aftion and re-aftion on and through the me¬ 
dium of fpace, or their momenta, are equals and, as the 
earth revolves at the fame time round its own axis, and 
the centres of both thefe rotations do not accord, fo li- 
brations of the movable fluids of the earth reftore the ba¬ 
lance, and occafion what are called Tides of the fea and 
atmofphere, correfponding in direction and quantity with 
the varied pofitions of thofe two centres of terreftrial ro¬ 
tation, in relation of both to the fun or to the line of the 
earth’s orbit. Thus, at the new and full moon, the dif¬ 
tances are greateft from the orbit, and then the ofcilla- 
tions are greateft; and at the quarters they coincide with 
the orbit,and then theofcillations are weak continuations 
of former ofcillations. 
9. Hence alfo it is that the centre of the maffes of the 
earth and moon are carried round the fun, by their reci¬ 
procal aftions and re-aftions on and through the medium 
of fpace, created by the probable and admitted motion of 
the furi around the centre of the mafles of the folar fyf- 
tem ; the unequal dift'ufion and aftion of the movable 
fluids in the two hemifpheres, caufing the Earth, at dif¬ 
ferent periods of its orbit, to lengthen and fhorten its 
virtual lever, and to defcribe an elliptic orbit. 
10. The general motions of the earth, as an aggregate, 
are the fources of all the relative morions which take 
place upon it; and every motion on the earth is but an 
appropriation, re-aftion, or mechanical transfer, of part 
of the motions of the earth. If the earth were at reft, 
there could be no motion to transfer; confequently, there 
could be neither aftion nor re-aftion, nor any kind of ani¬ 
mal power or loco-motion, nor any aggregate motion or 
projeftile force. 
11. All the parts of the earth confolidate and fall to¬ 
wards the centre, becaufe every part is the patient of the 
rotatory force, which gives them ftation proportioned to 
their rarity, and of the paramount orbicular force which 
impels all the denfeft maffes towards the line of motion; 
and alfo becaufe the centre cf the earth is the centre of the 
cmnbinedforces or ?notions of all the united maffes. 
12. An unattached body, as a ftone let fall or projefted, 
returns to the earth, becaufe, at the time when it was un¬ 
attached or projected, it was the patient of the Earth’s 
motions, and the force which raifed it ceafes to aft when 
it was let fall, or is foon imparted to the air; and becaufe 
the common force which revolves the earth and atmofphere 
cannot revolve a ftone in the circle in which it revolves 
the air. In every ftratum of the terreftrial mafs, the den- 
flty, multiplied by the velocity of rotation, is, or ought to 
be, equal; and, if unequal, then bodies rife or fali accor¬ 
dingly: and hence in air a balloon rifes, a bubble fwirus, 
and a ftone falls. 
13. As it is with the earth, fo it is with all the planet¬ 
ary bodies: they fwim in the medium of fpace, furrounded 
by atmofpheres, which fine off like the down on the feeds 
of thiftles: they are, confequently, moved by very deli¬ 
cate impulfes, are turned on their axes by flight combina¬ 
tions, and eafily aft upon and receive the re-aftion of 
their fatellites. Like fhips in motion, they impart their 
impulfes to bodies in contaft with them ; and thofe bo¬ 
dies become, in confequence, the patients of all their mo- 
lions, while every part, in its own re-actions, neceflarily 
107 
refpefts the common centre of the motions of the aggre¬ 
gate. Comets move in very eccentric orbits, becaufe 
they do not move in the plane of the fun’s motions or im¬ 
pulfes, which is nearly that of the lefs eccentric planets. 
14. When percuflion or collifion does not produce an 
equal quantity of aggregate motion in a proportionate 
change of place in the aggregate ; or when the motion 
received cannot be transferred by dift'ufion, as when a piece 
of iron, laid on an anvil, receives the motion of a ham¬ 
mer, or when two pieces of wood are rubbed together, an 
inteftine re-aftion of the atoms in the iron and wood 
takes place, accompanied by the perception of heat, and 
by a feries of phenomena depending on the quantity of 
motion thus concentrated, and on the acceleration of the 
fame by reiterated blows, rubbings, or transfers of motion. 
15. This inteftine motion produces various phenomena 
of the feveral component atoms of the affefted body in 
regard to one another, and to the heterogeneous media in 
which they are fituated : thus, one quantity creates a per¬ 
ception of heat, another fenfibly imparts that perception 
to the atoms of the furrounding media, another converts 
the fixed mafs into fluids, an acceleration converts the 
fluids into diverging gas, and a further acceleration, 
which exceeds the radiating powers of the furrounding 
media, decompofes thofe media, exhibiting flame and in- 
tenfe heat, in the folidification of the oxygenous part of the 
media, and, producing fubtle radiations on the rare medium 
which fills fpace, thereby affefting the nerves of the eye, 
imbued with that medium, with the perceptions of light. 
16. The parting with each degree of atomic motion pro¬ 
duces a contrary feries of phenomena : thus gas, on part¬ 
ing with its heat or atomic motion to other bodies, 
becomes fluid ; and fluids, by parting with their heat or 
excited motion, become folids ; and the dift’ufion of heat 
or atomic motion on fuch re-converfion is fenfible, when 
the oxygenous part of atmofpheric gas, folidified by re- 
fpiration, gives out what is called animal heat; and when 
the fame, folidified by combuftion, or reduced in volume 
by coinpreflion, gives out heat, and excites the pulfations 
of light. 
17. Refiftance is a phenomenon of parting with recei¬ 
ved motion. A body faid to be refilled, is merely parting 
with its motion to the atoms which it encounters in the 
media within which it moves; and, as it continues to 
part with its motion to the radiating atoms, its grad ually- 
diminilhed energy of motion is, in vulgar language, faid 
to be deftroyed by refiftance. 
18. Friftion, like refiftance, is a mere phenomenon of 
parting with motion, but to a fixed body inftead of a 
fluid ; and, being a variation of percuflion, or of transfer 
of motion without change of place, it produces flmilar 
phenomena of inteftine atomic motion or heat, which, 
when continued or accelerated, produces all the other 
phenomena of accelerated atomic motion or heat. 
19. Cryftallization is a mere effeft of parting with ato¬ 
mic motion, in certain connexions with, or relation to, 
the atoms of the furrounding media. 
20. The phenomena of eleftricity, galvanifm, &c. con- 
fift in feparations or mechanical decompofitions of the 
component gazeous atoms of plates of eleftrics, connected 
and con den led on their oppofed furfaces by furfaces of 
non-eleftrics: the re-union of which feparated ftrata 
through a Angle point of conduit produces intenfe phe¬ 
nomena of atomic motion. Thus, glafs is coated by tin- 
foil, air by metal conduftors, the atmofphere by clouds 
and earth, and acids in galvanifm by metallic plates; and 
the eleftric or galvanic power is within the intervening 
eleftrics, or on their furfaces. 
i zi. Loofe light bodies placed on the furface of an elec • 
trifled ftratum of coated air, prefent nearer furfaces to 
the oppolitely-affefted furface; and the bodies being- 
light are patients of the force exerted within the ftratum 
to reftore the difturbed equilibrium of its furfaces; and 
therefore, by the energy exerted on their furfaces, they 
are alternately wafted between the affefted furfaces of 
the ftratum, creating phenomena which, in the language 
