542 
A T T R A 
power. The laws, phenomenon, &c. of attraction, form the 
chief fubjeCt of Sir Ifaac Newton’s philofophy, being the 
principal agent of nature, in almoft all her operations. 
The principle of attraction, in the Newtonian fenfe, 
was firft furmifed by Copernicus. “ As for gravity, fays 
he, I confider it as nothing more than a certain natural ap¬ 
petence ( appetentia) that the Creator has imprefted upon 
all the parts of matter, in order to their uniting and co- 
alefcing into a globular form, for their better prefervation; 
and it is probable that the fame power is alfo inherent in 
the fun and moon, and planets, that thofe bodies may con- 
ftantly retain that round form in which we fee them.” De 
Revol. Orb. Ccelejl. lib. i. c. 9. Kepler calls gravity a cor¬ 
poreal and mutual affeClion between fimilar bodies, in or¬ 
der to their union. AJl. Nov. inlntrod. And he pronounced 
more pofitively that no bodies whatever were abfolutely 
light, but only relatively fo ; and confequently that all 
matter was fubjefted to the power and law of gravitation. 
The fir ft in this country who adopted the notion of at¬ 
traction, was Dr. Gilbert in his book De Magnete ; and 
the next was the celebrated lord Bacon, in his Nov. Organ. 
lib. ii. aphor. 36,45,48. Silv. cent. i. exp. 33 ; alfo in his trea- 
tife De Motu, particularly under the article of the 9th and 
13th forts of Motion. In France it was received by Fer¬ 
mat and Soberval; and in Italy by Galileo and Borelli. 
But, till Newton appeared, this principle was very imper¬ 
fectly defined and applied. 
It muft be obferved, that though this great author 
makes ufe of the word attraction, in common with the 
fchool philofophers, yet lie very ftudioully diftinguifties 
between the ideas. The ancient attraction was conceived 
to be a kind of quality inherent in certain bodies them- 
felves, and arifing from their particular or fpecific forms. 
But the Newtonian attraction is a more indefinite princi¬ 
ple ; denoting not any particular kind or mode of aCtion ; 
nor the phyfical caufe of fuch aCtion ; but only a general 
tendency, a conatus accedendi, to whatever caufe, phyfical 
or metaphyfical, fuch effeCt be owing ; whether to a pow¬ 
er inherent in the bodies themfelves, or to the impulfe of 
an external agent. Accordingly, that author remarks, in 
his Philof. Nat. Prin. Math. “ that he ufes the words at¬ 
traction, impulfe, and propenfion, to the centre, indifferently ; 
and cautions the reader not to imagine that by attraction 
he expreifes the modus of the aCtion, or its efficient caufe, 
as if there were any proper powers in the centres, which 
in reality are only mathematical points; or as if centres 
could attract.” Lib.i.p.5. So, he “ conliders centri¬ 
petal powers as attractions, though, phyfically fpeaking, 
U were perhaps more juft to call them impulfes. Ib. p. 
147. He adds, “ that what he calls attraction may pof- 
fibly be effected by impulfe, though not a common or 
corporal, impulfe, or after fome other manner unknown 
to us.*’ 0 
Attraction, if conlidered as a quality arifing from the 
. fpecific forms of bodies, ought, together with fympathy, 
antipathy, and the whole tribe of occult qualities, to be 
exploded. But, when thefe are fet afide, there will re¬ 
main innumerable phenomena of nature, and particularly 
the gravity or weight of bodies, or their tendency to a 
centre, that argue a principle of aCtion feemingly diftinCt 
from impulfe; where, at leaft, there is no fenfible impul¬ 
sion concerned. Nay, what is more, this action, in fome 
refpeCts, differs from all impulfion we know of; impulfe 
being always found to aCt in proportion to the furfaces of 
bodies ; whereas gravity aCts according to their folid con¬ 
tent, and confequently it muft arife from fome caufe that 
penetrates or pervades the whole fubltanee of it. This 
unknown principle, unknown we mean in refpect of its 
caufe, for its phenomena and effeCts are moft obvious, 
with all its fpecies and modifications, is called attraction ; 
being a general name, under which may be ranged all 
mutual tendencies, where no phyfical impulfe appears, 
and which confequently cannot be accounted for upon any 
known laws of nature. And hence arife divers particular 
kinds of attraction J as gravity, magnetifm, electricity, &c. 
C T I O N. 
which are fo many different principles, acting by different 
laws; and only agreeing in this, that we do not perceive 
any phyfical cattles of them : but that, as to our fenfes, 
they may really arife from fome power or efficacy in fuch 
bodies, by which they are enabled to aCt even upon dif- 
tant bodies ; though our reafon abfolutely djifallows of any 
fuch aCtion. 
Attraction may be divided, with refpect to the law it 
obferves, into two kinds. 1. That which extends to a 
fenlible diftance. As the attraction of gravity, which is 
found in all bodies; and the attraction of magnetifm and 
eleCtricity, found only in particular bodies. The feveral 
laws and phenomena of each, fee under thofe refpeCtive 
articles. 
The attraction of gravity, called alfo among mathema¬ 
ticians the centripetal force, is one of the greateft and moft 
univerfal principles of all nature. We fee and feel it ope¬ 
rate on bodies near the earth, and find by obervation that 
the fame power (i. e. a power which aCts in the fame man¬ 
ner, and by the fame rules, viz. always proportionally to 
the quantities of matter, and inverfely as the fquares of 
the diftances) does alfo obtain in the moon, and the other 
planets, both primary and fecondary, as well as in the co¬ 
mets ; and even that this is the very power by which they 
are all retained in their orbits. And hence, as gravity is 
found in all the bodies which come under our observation, 
it is eafily inferred, by one of the eftabliftied rules of phi- 
lofophizing, that it .obtains in all others. And fince it is 
found to be proportional to the quantity of matter in any 
body, it muft in every particle of it: and hence it is prov¬ 
ed that every particle in nature attracts every other parti¬ 
cle. From this attraction arifes all the motion, and con¬ 
fequently all the mutation, in the great world. By this 
heavy bodies defeend, and light ones afeend : by this pro¬ 
jectiles are directed, vapours and exhalations rife, and 
rains fall : by this rivers glide, the ocean fwells, the air 
prelfes, See. In fiiort, the motions and forces arifing from 
this principle, conftitute the fubjeCt of that extenfive 
branch of mathematics, called mechanics or Jlatics, with 
the parts or appendages of it, as hydroftatics, pneumatics, 
hydraulics, See. 
2. That which does not extend to fenlible diftances. 
Such is found to obtain in the minute particles of which 
bodies are compofed, attracting each other at or extreme¬ 
ly near the point of contaCf, with forces often much fu- 
perior to that of gravity, but which at any diftance de- 
creafe much fafter than the power of gravity. This power 
a late ingenious author calls the attraction of cohcfion, as 
being that by which the atoms or infenfible particles of 
bodies are united into fenfible mafles. This kind of at¬ 
traction owns Sir Ifaac Newton for its difeoverer ; as the 
former does for its improver. The laws of motion, per- 
cuflion, &c. in fenfible bodies, under various circum- 
ftances, as falling, projected, &c. afeertained by the later 
philofophers, do not reach thofe more reclufe int.eftine 
motions, in the component particles of the fame bodies, on 
which depend the changes in the texture, colour, proper¬ 
ties, See. of bodies. So that our philofophy, if it were 
only founded on the principle of gravitation, and even 
carried as far as this w'ould lead us, would ftill be very 
deficient. But, betides the common laws of fenfible 
maftes, the minute parts they are compofed of are found 
fubjeCt to fome others, which have but lately been notic¬ 
ed, and are even yet imperfeClly known. Newton him- 
felf, to whofe happy penetration we owe the hint, limits 
himfelf with eftabliffiing that there are fuch motions in 
the minima naturae, and that they flow from certain pow¬ 
ers or forces, not reducible to any of thofe in the great 
world. He fliews that, by virtue of thefe powers, “ the 
fmall particles aCt on one another even at a diftance ; and 
that many of the phenomena of nature refult from it. 
Senfible bodies, we have already obferved, aCt on one ano¬ 
ther divers ways ; and, as we thus perceive the tenor and 
courfe of nature, it appears highly probable that there may 
be other powers of the like kind ; nature being yery uni¬ 
form 
