F L U 
47 ! 
FLU 
intelligences and geniufes, and he called together troops 
of fpirits from the four winds, to whom he committed the 
charge of difeafes. He conceived a harmony between the 
macrocofm and the microcofm, or the world of nature 
and of man. His extravagances were thought worthy of 
being refuted, by Kepler, Merfennus, and Gaffendi, the 
latter of whom wrote an Examcn Philofophiee Fluddiance. 
One of Fludd’s works, the Nexus utriufque Cojmi , is illuf- 
trated by fome Angular prints. 
FLUE, f. [a word of uncertain etymology, probably 
derived from jlezu or jly. ] A fmall pipe or chimney to con¬ 
vey air, heat, or fmoke. Soft down or fur, fuch as may 
fly in the wind, 
FLUF. L'LIN, /. in botany. See Antirrhinum, and 
Veronica. 
FLU'ENCY,yi The quality of flowing ; fmoothnefs ; 
freedom from harfltnefs or afperity.— Fluency of numbers, 
and moft exprellive figures for the poet, morals for the 
ferious, and pleafantries for admirers of points of wit. 
Garth. —Readinefs ; copioufnefs; volubility.—The com¬ 
mon jluency of fpeech in many men, and moft women, is 
owing to a fcarcity of matter, and a Icarcity of words ; for 
whoever is matter of language, and hath a mind full of 
ideas, will be apt in fpeaking to hefitate upon the choice 
of both. Swift. 
We reafon with fuch jluency and fire, 
The beaux we baffle, and the learned tire. Ticliel. 
Affluence; abundance. Thisfenfe is ohj'oletc. 
God riches and renown to men imparts, 
Even all they wifli ; and yet their narrow hearts 
Cannot fo great a jluency receive, 
But their fruition to a firanger leave. Sandys. 
FLU'ENT, adj. [jluens, Lat.] Liquid.—It is not mal¬ 
leable ; but yet it is not fluent, but ttupefied. Bacon. — 
Flowing; flowing in motion; influx.—Motion being a 
jluent thing, and one part of its duration being independent 
upon another, it doth not follow that becaufe any thing 
moves this moment, it mutt do fo the next. Ray. —Ready ; 
copious ; voluble.—Thofe have fome natural difpofi- 
tions, which have better grace in youth than in age, fuch 
as is a fluent and luxurious fpeech. Bacon. 
FLU'ENT, j. Stream; running water : 
Confiding in their hands, that fed’lotts ftrive 
To cut th’ outrageous fiuent ; in this diftrefs, 
Ev’n in the fight of death. Philips. 
FLU'ENT, or Flowing Quantity, in the dodirine 
of fluxions, is the variable quantity which is confidered 
as increafing or decreafing ; of the fluent of a given 
fluxion, is that quantity whole fluxion being taken, ac¬ 
cording to the rules of that dodirine, fhall be the lame 
with the given fluxion. See Fluxions. 
FLU'ENTLY, adv. With ready flow ; volubly ; 
readily ; without obftrudlion or difficulty. 
FI.U'ID, adj. [jluidus, Lat. jluide, Fr.] Having parts 
eafily feparable.—If particles flip eafily, and are of a fit 
fize to be agitated by heat, and the heat is big enough 
to keep them in agitation, the body \s fluid \ and if it be 
apt to ftick to things, it is humid. Newton. 
FLU'ID,/! Any thing not fo lid. [In phylic.] Any 
animal juice : as the blood.—Confider how luxury hath 
introduced new difeafes, and with them, not improbably, 
altered the courfe of the f.uids. Arbuthnot. 
FLUI'D BODY, that whole parts yield to the fmalleft 
force imprelfed, and by yielding are eafily moved among 
each other ; in which fenfe it (lands oppoled to a folid. 
This is the definition of a perfett fluid : if the fluid re¬ 
quire fome fenfibl.e force to move its parts, it is imperfcEl 
in proportion to that force ; fuch are perhaps all the 
fluids we know of in nature. That fluids have vacuities 
in their fubttance is evident, becaufe certain bodies may 
be diflolved in them without increafing their bulk. Thus, 
water will dilfolve a certain quantity of fait ; after which 
it will receive a little fugar, and after that a little alum ; 
and all this without increafing its firft dimeniions. Which 
Ihews that the particles of thefe folids are fo far feparated 
as to become Imaller than thofe of the fluid, and to be 
received and contained in the interttices of them. 
Fluids are either elattic, fuch as air; or nor-elattic, 
as water, mercury, &c. Thefe latter occupy the fame 
fpace, or are of the fame bulk, under all preiiures or 
forces ; but the former dilate and expand themfelves 
continually by taking off the external prefliire from them ; 
tor which reafon it is that the denlity and elafticity of 
fuch fluids, are proportional to the force or weight that 
compreffes them. The dodirine and laws of fluids are of 
the greateff extent in philofophy : the properties of elattic 
fluids conftituting the dodirine of Pneumatics; thofe 
of the non-elaftic ones, that of Hydrostatics ; and their 
motions, Hydraulics. For which fee thofe refpedtive 
articles. 
FLUID'ITY,yi \_jhdditi , Fr. from fluid.'] The quality 
in bodies oppofite to liability ; want of coherence between 
the parts.—Fluidity is to be carefully diftinguilhed from 
liquidity or humidity, which latter implies wetting or ad¬ 
hering. Thus, air, ether, mercury, and other melted 
metals, and even fmoke and flame itfelf, are fluid bodies, 
but not liquid ones ; vvhiltt water, beer, milk, urine, &c. 
are both fluids and liquids at the fame time. The nature 
and caufes of fluidity have been varioufly affigned. The 
Gaflendifts, and ancient corpufcularians, require only 
three conditions asmeceffary to it, viz. a fmallnefs and 
fmoothnefs of the particles of the body, vacuities inter- 
fperfed between them, and a fpherical figure. The Car- 
tefians, and after them Dr. Hook, Mr. Boyle, &c. befide 
thefe circumttances, require alfo a certain internal or in— 
teftine motion of the particles as chiefly contributing to 
fluidity. Thus, Mr. Boyle, in his Hiftory of Fluidity, 
argues from various experiments: for example, a little 
dry powder of alabatter, or platter of Paris, finely lifted, 
being put into a velfel over the fire, foon begins to boil 
like water ; exhibiting all the motions and phenomena of 
a boiling liquor: it will tumble varioufly in great waves 
like that; will bear ftirring with a ftick or ladle like that, 
without refitting; and if llrongly ftirred near the fide of 
the velfel, its waves will apparently dafli againft it: yet 
it is all the while a dry parched powder. The like is ob- 
ferved in fand ; a dilh of which being fet on a drum-head, 
brifkly beaten by the flicks, or on the upper (lone of a 
mill, it in all refpedts emulates the properties of a fluid 
body. A heavy body, ex. gr. will immediately fink in it 
to the bottom, and a light one emerge to the top : each 
grain of fand has a conftant vibratory and dancing mo¬ 
tion ; and if a hole be made in the fide of the dilh, the 
fand will fpin out like water. 
The Cartefians .bring divers confiderations to prove 
that the parts of fluids are in continual motion : as firlf. 
The change of folids into fluids, ex.gr. ice into water, 
and vice verfa ; the chief difference between the body in 
thofe two ftates confiding in this, that the parts,, being 
fixed and at reft in the one, refill the touch ; whereas in 
the other, being already in motion, they give way to the 
flighted impulte. Secondly, The effedls of fluids, which 
commonly proceed from motion : fuch are the inhumation 
of fluids among the pores of bodies ; the foftening and 
difl’olving hard bodies; the adtions of corrofive men- 
llruums ; &c. belides that no folid can be brought to a 
ftate of fluidity, without the intervention of fome moving 
or moveable body, as fire, air, or water. Air, the fame 
gentlemen hold to be the firft fpring of thefe caufes of 
fluidity, it being this th.it gives motion to fire and water, 
though itfelf receives its motion and adlion from the ether, 
or fubtle medium. 
But Boerhaave pleads ftrenuoufly that fire is the firft 
mover, and the caufe of all fluidity in other bodies, as 
air, water, Sic. without this, he Ihews that the atmofphere 
itfelf would fix into one lblid mafs. And in like man¬ 
ner, Dr. Black mentions fluidity as an effiedt of heat. 
The different degrees of heat which are required to bring 
different bodies into a ftate of fluidity, he fuppofes.may 
depend on fome particulars in the mixture and compofi- 
ticn 
