Page:Cyclopaedia, Chambers - Volume 2.djvu/946

 V E I

In their Progrefs, uniting their Channels as they approach it, they, at laft, all form three large Veins, or Trunks, viz.

The Vena Cava defcendens, which brings the Blood back from all the Parts above the Heart. See Cava.

The Vena Cava afcendens, which brings the Blood from all the Parts below the Heatt. See Heart.

And the 'Porta which carries the Blood to the Liver. See Porta, £5?c.

The Anaflomafis, or Inofculation of the Veins and Ar- teries, was firft feen by the Microfcope, in the Feet, Tails, ££c. of Frogs, and other amphibious Animals, by Lee-wen- hoeck; but has fince been obferv'd in other Animals, particu- larly the Omentum ofa Cat, by Mr. Cowper,&.c. SeeANAs- tomasis, Circulation, lye.

The Coats of the Veins Site, four, the fame with thofe of the Arteries; only the mufcular Coat is as thin in all the Veins, as it is in the Capillary Arteries; the Preffure of the Blood againft the Sides of the Veins, being lefs than that againft the Sides of the Arteries; becaufe the Force of the Heart is much broke in the Capillaries. See Phlebotomy.

In the Veins there is no Pulfe, becaufe the Blood is thrown into them with a continued Stream, and becaufe it moves from a narrow Channel to a wider. See Pulse.

But they have a Perittaltick Motion, which depends on their mufcular Coat. See Peristaltic.

The Capillary Veins unite with one another, as has been faid of the Capillary Arteries; only their Courfe is direffly oppofite : for inftead of a Trunk diftributcd into Branches and Capillaries, a Vein is a Trunk form'd out of a Con- courfe of Capillaries. See Capillary.

In all the Veins which arc perpendicular to the Horizon, excepting thole of the Uterus and the Porta, there are (mall Membranes, or Valves : fometimes there is only one, fometimes there are two, and fometimes three, placed toge- ther, like fo many half Thimbles ftuck to the Sides of the Veins, with their Mouths towards the Heart.

Thefe, in the Motion of the Blood towards the Heart, are prefs'd clofe to the Sides of the Vein; but ftiut the Veins, againft any re-flux of the Blood that way from the Heart, and thereby fuftain the Weight thereof in the great Trunks. See Valves.

_ The Veins are diftinguiflYd, with refpect to their Situa- tion, into fuperior and inferior, afcending, and defcending; right, as the Mefenteria, and left, as the Splenic Branch; internal, as the 'Ba/ilica; and external, as the Humeral.

Many of them, likewife, acquire Denominations from the Parts wherein they are found; as, the Jugulars, Phreni- tic, Renal, Iliac, Hypogaftric, Epigaftric, Axillary, Crural, XJnibilical, Sural, Sciatica:, Saphente, Medians, Cephalic, Thoracic, Subclavian, Intercoflal, Coronal, Diaphragmatic, Cxcal, Hemorrhoidal, Cervical, Thymal, Mamillary, Gaf- tric. Stomachic, Epiploic, Splenic, Sec.

They are alfo dittinguifiVd from their particular Offices, into Spermatic, Emulgent, &c. all -which fee exhibited in

Plate Anatomy and their particular 'Definitions under

their proper Articles.

Vein is alfo apply'd to the Streaks, or Waves of divers Colours, appearing on feveral forts of Woods, Stones, £5?c. as if they were really painted; and which the Painters fre- quently imitate in painting Wainfcots, £5?c.

Marble is generally full of fuch Veins. See Marble.

Lapis Lazuli has Veins like Gold. See Lapis.

Ovid, fpeaking of the Metamorphofes of Stones into Men, fays,

£>tiie modi vena fait, fub eodem nomine manfit.

Veins, in Stones, are a Defefl, proceeding ufually from an Inequality in their Confidence as to hard, and foft ■ which makes the Stone crack, and fhiver in thole Parrs.

Vein, is alfo applied, in the fame Senfe with Stratum, to the different Difpofitions and Kinds of Earth met withal in digging. See Stratum.

Thus, we fay, a Vein of Sand, another of Rock, (gc. a Vein of Ocher, Vitriol, Allom, Calamine, Coal, iSc.

Mineral Waters acquire their different Qualities by paffing thro' Veins of Vitriol, Sulphur, ££?c. See Mineral.

In the fame Senfe, we fay, a Vein of Gold, Silver, Ouick- filver, cifc. meaning certain Parts of the Earth, wherein the Oar or Glebe of thole Metals is found; and which is diflri- butcd into divers Branches, like the Veins in the Body. See Oar, Mine, $$c.

T'avernier gives us a Defcription of the Veins in the Diamond Mines in Golconda, with the manner of digging them. See Diamond.

In digging of Coal-Pits, they meet with a Variety of Veins, the Order, tSc- of which, is different in different Places : In the 'Philofbfhical Tranfatlions, N" 3*0. the Veins in thofe famous Coal-Mines at Mendip, in Somerfet- Jhire, are obferved to be, (below the Turf, or Loam, or Malm, a reddim .Fire-ftone; the Coal Clives, which is a blackifri Rock;) the fflinking Vein, a hard Coal for me- chanic Ufes; five Foot below which, is the Catfhead Vein,

C 289]

V E L

22 Foot thick, mtermix'd with Lumps of Stone; at a like d.ftance below which, is the three Coal Vein, divided into

Tl £ °, C ° al> and about ,hree Foot thick -

lhe Veins hitherto mention'd are frequently work'd in the fame Pit.- The next is Peaiv Vein, which is inter- mix d with Cockle- /hells and Fern Branches, ufually wrought in a leparate Pit: tho its depth below the three Coal Vein be only about five Foot, yet the Cliff between is very hard, and liable to Water : This Vein is about a Yard thick \ and the like diflance below it, is the Smith's Coal Vein : beneath which is the Shelly Vein; and under that a Vein

«" Inches, little worth, and feldom wrought. See Coal.

1 he lame Veins are found in a Place feven or eight Miles apart;— AH the Veins lie obliquely, or (helving, like the fide of a Houfe : The Obliquity, or Pitch, as they term it, is about 22 Inches in a Fathom; which, when it rifes to the Land, is call'd Crop, and in fome Places Baffeting.

In digging to the South-weft, they oft meet with Ridges, which caufe the Vein to trap up; i. e. being cut off by toe Ridges, they find it over their Heads, when they are thro the Ridge : On the contrary, working thro' a Ridge to the North eaft, they fay it traps down.; i. e. rhey find it under their Feet.

VF.JOURS, in Law, are thofe fent by the Court to take View of any Place in queflion, for the better Decifion of the Right. See View.

It is alfo ufed for thofe fent to view fuch as Effoign them- lelves De malo leSi; whether in truth they be fuch as that they cannot appear, or whether they counterfeit.

VELAMEN, in Surgery, the Bag, Skin, or Bladder of an Impofthume, or Swelling. See Cystis

VELAMENTUM

jcinum, a Name fome Anato- mifts give to the velvet Membrane, or Skin of the Interlines. See Intestine.

VELARIUS, in Antiquity, an Officer in the Court of the Roman Emperors.

The Velarii were a kind of Uftiers, whofe Poft was be- hind the Curtains, Vela, in rhe Prince's Apartments; as that of the Chancellors was at the Entry of the Baluftrade, Cancelli; and that of the Ofliarii at the Door.

The Velarii had a Superior, of the fame Name, who commanded them; as we find in two Infcriptions, quoted by Salmafins in his Notes on Vopifcus; and by a third in Gruter. The firft is,

D. M.

TI. CL. HALLUS

PROPOSITUS VELA RIORUM—

DOMUS AUGUSTANAE

FEC. SIBI FT FILIIS SUIS L. L.

POST. EORUM.

Salmafius, and others, for HALLUS, which is in the Stone whereon the Inlcription is, ax Rome, put THALLUS : Tho we find mention of the fame Hallus as a Samaritan by Nation, and <fiberius's Freedman, in Jofephus; which fliews that the Velarii and their Chief were very antient Of- ficers, and in uje among the firft Emperors.

VELlTES*!n rhe Roman Army, a kind of antient Sol- diery, who were arm'd with a Javelin, a Caflc, Cuiraffe, and Shield.

VELLEITY, in the School Philofophy, is defined by fome, to be a languid, cold, and remifs Will. See Will.

Others fay, it implies an Impotency of obtaining what we require : Others will have it a flight Defire for fomething, which a Perfbn does not matter much, or is too indolent to leek : as, Cams amat Pifiem, fed non vutt tangere Lym- pham.

VELLICATION, among Phyficians, the Act of Twitch- ing.

Vellications are particularly ufed for a fort of hidden Con- vulsions that happen to the Fibres of the Mufcles. See Fibre, and Convulsion.

VELOCITY, in Mechanicks, Swiftnefs; is that Affec- tion of Motion, whereby a Moveable is difpofed to run over a certain Space in a certain Time. See Motion.

It is alfo call'd Celerity; and is ftill proportional to the Space moved. See Celerity.

The greateft Velocity wherewith a Ball can defcend, by virtue of its fpecific Weight, in a refilling Medium, is that which the fame Ball would acquire by falling in an unrefif- ting Medium, thro' a Space which is to four thirds of its Diameter, as the Denfity of the Ballto the Denfity of the Fluid. See Descent.

Huygens, Leibnitz, Bernoulli, Wblfius, and the foteign Mathematicians, hold that the Momenta, or Forces of fall- ing Bodies, at rhe End of their Falls, are as the Squares of their Velocities into the Quantities of Matter; the En- glifh Mathematicians, on the contrary, maintain 'em to be as the Velocities themfelves into the Quantities of Matter. See Momentum.

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