V A P
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Sometimes they are made of Brafs cover'd over with Lea ther, and furnilh'd with a fine Spring, which gives way up- on a Force apply'd againft it: bur, upon the c'eafing of that; returns rhe Valve over the Aperture. See Pump, iSc.
Confiautine Parole, a Boulognefe, and Phyfician of Gre- gory XIII. who dy'd in r;jo, was rhe fir't who cbferv'd the Valve in the Colon. Bart. Bujlacbw, a Native of San Severino in Italy, difcover'd, about the fame time, Valve at the Orifice of the Coronary Vein, and that remark- able one at the Orifice of the lower Trunk of the Vena Cava, near rhe right Auricle of the Heart : Tho he did not take it for a Valve, but merely for a Membrane.
Sig. Lanci/i, Phyfician to the late Pope, who firft publi (h'd . Eujlachios Works, takes the Ufe or this Valve to be to or from dry Bodies, as Sulph prevent the Blood of the upper Vena Cava from Unking and other Authors, better dill with too much violence again!! that of the lower : And Monfieur Win/low, who has confider'd it very diligently in the Memoirs of the Royal Academy of Sciences, is^much of the fame Opinion.
But as it gradually dwindles in Children, amd at lcngrh becomes quire loft in Adults, ftill diminifhing as the fora- men Ovale does ; it fliould feem ro have fome other Office ; and that, chiefly, regarding the Circulation of the B.ood in the Fxtus.
In eft'eft, by means hereof, M. Win/low reconciles rhe two opposite Syftems of rhe Circulation of the Biood in the Fxtus, delivcr'd under the Atticle Circulation. See Circu- lation of the Blood ; and Foetus
VALVULA, Valve. See Valv
VAR
We alfo ufe the Term Vapbnr-Baih; .when a fick Per- ifln is made to receive rhe Vapours arifing from fome liquid Matter placed over a Fire. See Bath.
VAPOUR; in Meteorology, a thin Veficle of Water or ether humid Matter, fill'd or inflated with Air ; which be- ing rarefy d to a certain degree by the Aflion of Heat, af- cends to a certain height in the Atmofphete, where it is the fufpended, till it return in form of Rain, Snow, or the like. See Rain, and Snow:
An Affemblage of a Number 6f Particles, or Veficles of
Vapour, conflitutes what we call a Cloud. See Cloud.
Some ule the lerm ;'«/'«»-, indifferently'; for all Fumes
med, either from moift Bodies, as Fluids of any kind ;
&c. But Sir /. Newton-,
Itinguifh between humid and
tter Exhalation. See Exhala-
dry Fumes, calling the
TION.
For the Manner -therein VApours are rais'd, 'and again precipitated ; fee Dew, Rain, FIeat, Coed, and Baro- meter.
For the Effett of Vapour in the Formation of Springs, &c. See Spring, and River.
The quantity of Vapour rais'd from rhe Sea by the Warmth of the Sun, is far grca er than one would imagine. Dr. Hr-.Ucy has attempted 10 ellimate it.
In an Experiment made with that view, and defcribed irt the 'Pbilofoykical TranfdBions, he found that a Quantity of Water no warmer than Air in Summer, loft in Vapour in the Space of two Hours, no lefs than ;
T) j • , ' . , %z zzy ' u^|-v-i .11 ucuiu : x^uw lur ,- m two Hours taking i
<rXTtr<t 7a'v e L 'f °p the FT? ^ etWCt " the ™'^ h '" *» 'Welve Hours that S
Icfte* and the firft Vermicular Procefs of the Cerebellum : Day, it will wife J, of an Inch from the Su
Irs Subftance is medullary. Its Ufe is to prevent the Lymph Sea.
-.;,.!:!-. ; ." - Dart of an Inch The great Valve, in-Latin; Valvula Major, is the upper in depth": Now, for .;.. in'two Hours, takb [for rhe eafier
bun is up each .......... ..^ Surface of the
ry. Its Ule is to prevent the Lymph Sea. from falling 01, the Nerves at the Bake of the Cranium. On this Suppofition, every 10 fquare Inches of the Sur-
Ir the jfefmum and Ileum, the inner Tunic being lar- face of Water, yield in Vapour, per Diem, a Cubic Inch of S,"*"" 1 ul^^ m l Ch - Cm r m ^ Ki ', the lo ° fe ! old i°. f Wa »5 -d each fquare Foot/ half a Wine Pint ; every
Space of four Foot fquare, a Gallon ; a Mile fquare, 691$
Tuns ; a fquare Degree, I'uppofed of Co Englijb Miles, will
evaporate 35 Millions of Tuns • And if the Mediterranean
tees long, and four broad, Allow-
Places where it is broader, by
. there will be 160 fquare Degrees
and confcquenrlv the whole Mediterra.npan mnft
be eafily propell d towards the Glands: Which argues, lofe in Vapour, in a Summer's Day, at kaft Z l£
which, have been thought in fome meafure to do the Of- fice of Valves ; and have therefore been call'd Valvule • Connivcntes.' Drake'.! Anat. p. 49.
admit of a Reflux towatds the Interlines : tho the Liquor at Sea
' that there are Valves in 'em, tho too minute to be fallible'
- to the Eye.' Id. ibid. p. 55.
The Word is form'd from the Latin Valve, folding Doors.
VAN, or Vast, or Vaunt, of the French, avant, or -tmmmt, hefore ; a Term ufed in Compofition with feve- ral Words in our Language.
VAN-Couriers, are Light-arm'd Soldicts, fent before to beat the Road, upon the Apptoach of an Enemy. See Re- connoitre.
Viu-Fojfe, a Ditch dug without the Counterfcarp, and ly^th'e Spi,
running all along the Glacis ; ufually full of Watet. See Ditch.
Van, or Vant, or VAvxr-Corps. See Corps.
Van-Gmtv^, is a Military Term, fignifying the firft Line of an Army, drawn up in Battalia.
It is the fame with the Front of an Army, and gives the firft Charge upon the Enemy. See Front
of Tuns.
And this Quantity of Vapour, tho very great, is only the Remains of another Caufe, which cannot be redu- ced to Rule ; we mean the Winds ; whereby the Surface of the Water is lick'd up, fomenmes falter than it exhales by the Heat of the Sun ; as is well known to thofe that have confider'd thofe drying Winds. See Evaporation.
VAPOURS, in Medicine, a Difeafe, call'd popularly rhe Hypo, or Hypochondriacal Difeafe ; and in Men, particular* "ken. Sec Spleen.
fubtile Vapour, fifing - particularly the Hy.
Tis fuppofed to be owing to a from the lower Parts of the Abdom
pocbondrium, to the Brain ; which it di'fturbs, and poffefles with wild, delirious, but generally difagreeable Imagina- tions. See Hypochondriacal llifeafe.
Vapours, fuppofed to be emitted from the Wotrib, in Wo- men, are what we otherwife call Htfterical Metlions, or Every Army is compos d of three Parts, a Van-guard, Suffocations, or Fits of the Mother. See Hysterica! sA- Hear-guard, and Main Body. Vapour-S^. See Vaporosum S '
VANES, on Mathematical Infttuments, are Sights made to move and Aide upon Crofs-ftaves, Fore-ilaves, ^Davis's Quadrants, tSc. See Cross-staff, Fore-staff, E?c. Vanes, or Fanes of Feathers.'! c „„SFeather Vanes of Windmills. S
VANILLA, or Banilla.
See-
Windmill.
aporosum Balneum.
VARI, in Medicine, little, hard, ruddy Tumors, whitilfl about the Tips, and of the fize of an Hemp. feed ; fre- quently found on the Face and Neck of young People • chief- ly fuch as are much addicted to Venery.
If the ted be very lively, the Cure is fomewhat difficult;
Chocolate,
It is alfo ufed to perfume Tobacco withal. See Tobacco.
It is fuppofed to ftrengthen the Brain, and Stomach ; to attenuate vifcid Humouts, provoke Urine, and the Menfes.
applied chiefly by the foreign Mathematicians, to fuch Quantities, as cither increafe, or diminifh, according as fomS other Quantity either increafes or.diminifhes.
Thus, the Semiordinates and AMciffes of a Circle, 85?^
VAPORATION in Chymiftry, a Term applied to the are Variable famines , becaufe, if the one increafe, thd Athon of Vapour See Vapour other increafes^kewife. See Sem.ordinate, C? C ,
The Chym.fts have a Bath call d a Vaporatory, or Sal- They are thus call'd, in comradiftinaion to conflant, 6r ,,e,tm Vaporattoms ot Vapons ; whereby the Warmth or given, or ftable Quantities ; which are always the fame, tho Flumid.ty of a Vapour is made to afl on fome other Body, others change ; as the Semidiameter of a Circle, which re-
- : ' he ™V r ™.°'°L. ead - See Balneum, Heat, c5c. mains rhe fame, tho theAbfciffes and Semiordinates increafe:
Variable Quantities, arc ufually denoted by the laft Let- ters of the Alphabet, xy z. See Quantity.
Our Engl'ijh Authors, inftcad of variable, and conflant Quantities, generally ufe the Terms fluent, and fiable Quantities. See Fluent.
The infinitely fmall Quantity whereby a variable Quan- tity is continually increasing, or dlminifhing, is called the Fluxion, or Difference s the Calculation Whereof, is the Sub- ath is very commodious for the d.ftilhng of jecl of the new Methodus DifferentialiS, or ffleSrae of is, and the drawing of Spirit of Winei Fluxions. See Differential, and FumoN.
VAPOROSUM Balneum, or VApouR-S<rr/.>, i n Chy miftry, a Term applied to a Chymilt's Bath, or Heat, wherein the Body is placed fo as to receive the Fumes of boiling Warer.
The Balneum Vtipor»fnm confifts of two Veffels, difofed over one another in fuch manner, as that the Vapour rais'd from the Water contain'd in the lower, heats the Matter en- clofed in the upper. See Heat
The Vapour-Bath odoriferous Water.
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VAKI-
