Page:Cyclopaedia, Chambers - Volume 2.djvu/956

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VERTEX, in Anatomy the Crown of the Head; or talons, but ufually hanging down with a kind of Lip, Or

that Fart fittiate between the Sinciput and Occiput. See turned fomething like the form of an Helmet : Four Seeds

u°' ,r TV, • c ■ , r. r , m r * ftcreach Flower; to which the Periantheum of the Flower

Hence, alio, Vertex is figuratively ufed for the Top of ferves inftead of a Capftlla Seminalis.

other Things.

Thus, the Vertex of a Cone, Pyramid, Conic Section, f£c. is the Point of the upper Extremity of the Axis ; or the Top of the Figure. See Cone, Pyramid, £$c.

Vertex of an Angle, is the angular Point ; or the Point A, (Tab. Geometry, Fig. 1.) wherein the Legs meet. See Angle.

Vertex of a Figure, is the Vertex of the Angle oppofite to the Bafe. See Figure.

Such is the Point M, (Tab. Geometry, Fig. io.l oppofite to the Bafe KL. See Base.

Vertex of a Curve, is the Point A, (Tab. Geom. Fig.;i.) .. from which the Diameter is drawn ; or the Interfeaion of Origanum, Majortma, Ocimum, Hon the Diameter, and the Curve. See Curve.

Vertex of a Gtaft, in Opticks, the fame with the Pole thereof. See Pole, Optic Glsfs, &c.

Vertex is alfo ufed in Altronomy, for that Point of Hea- ven perpendicularly over our Heads ; properly call'd the Ze- ?lith. See Zenith.

VERTICAL Circle, in Aflronomy, is a great Circle of the Sphere, paffing thro" the Zenith Z, and Nadir N, (Tab. A- ftrommy. Fig. 6.) and any other given Point in the Sur- face of the Sphere. See Circle, and Sphere.

Thus, the Meridian of any Place is a Vertical Circle. See Meridian, &c. _ All the Vertical Circles interact each other in the Ze- nith and Nadir. See Zenith, and Nadir.

The ufe of the Vertical Circles, is to meafure the Height of the Stars, and their Dillances from the ZeniTti, which is reckon'd on thefe Circles ; and to find their Eaftern and Weflern Amplitude, by obferving how many degrees the Vertical wherein the Star rifes, or fets, is dittant from the Meridian. See Altitude, Amplitude, &c.

The Vertical Circles are alfo called Azimuths. See Azi- muth.

'Prime Vertical, is that Vertical Circle, or Azimuth, which paffes thro' the Poles of the Meridian ; or which is perpendicular to the Meridian, and paffes thro' the Equinoc- tial Points. See Prime Vertical.

Vertical of the Sun, is the Vertical which paffes thro' the Centre of the Sun, at any Moment of Time.

Its ufe is in Dialling, to find the Declination of the Plane whereon the Dial is to be drawn ; which is done by obferving how many Degrees that Vertical is diilant from the Meri- dian, after marking the Point, or Line of the Shadow upon the Plane, at any time. See Declination.

Vertical Angles. Two Angles, as and x, (Tab. Geo- metry, Fig. 1 80 are faid to be Vertical, if the Legs of one of 'em, A E and E C, be only Continuations of the Legs of the other, DEandBE. See Angle.

Vertical 'Plane, in Perfpective, is a Plane perpendi- cular to the Geometrical Plane : paffing thro' the Eye, and cutting the Perfpeflive Plane at right Angles. See Plane.

Vertical 'Plane, in Conicks, is a Plane paffing thro' the Vertex of the Cone, and parallel to any Conic Section. See Plane, and Cone.

Vertical Line, in Conicks, is a right Line drawn on the Vertical 'Plane, and paffing thro' the Vertex of the Cone. See Line.

Vertical 'Dial, is a Sun-Dial, drawn on the Plane of a Vertical Circle ; or perpendicular to the Horizon. See Dial, and DiM J - i Plane.

Thefe are particularly call'd Oriental, Eaft, Occidental, Weft, Meridional, South, and Septentrional, or North Ver- ticals, when oppofed to one, or other of thele Cardinal Points of the Horizon. See East, West, £=fc.

When they don't look precifely to any of them, they are call'd 1)ecliiiers : And when their Plane, or Surface is not perfectly perpendicular, Recliners. See Decliner, Re- cliner, c5£.

Vertical "Point, in Aftronomy, the fame with Ver- tex, or Zenith.

Hence, a Star is faid to be Vertical, when it happens to be in that Point which is juft over any Place.

Vertical Line, in Dialling, is a Line on any Plane per- pendicular to the Horizon.

This is beft found and drawn on an erect and reclining Plane, by holding up a String and heavy Plummet fteadily, and then marking two Points of the Shadow of the Thread on the Plane, a good diftance from one another; and draw- ing a Line thro' thofe Marks. See Dialling.

VERTICILLATE Plants, are fuch as have their Flow- ers intermix'd with fmall Leaves, growing in a kind of Whirls about the Joints of a Stalk ; as Penny-royal, Hore- hound, iSc See Plant.

The peculiar Characteriftick of this Genus of Plants, ac- cording to Mr. Ray, is, that theit Leaves grow by Pairs, one juft againft another, on the Stalk : the Flower monope-

The fame Author makes two Species of thefe Verticillate Plants.

i°. The FruticofdS, or fuch whofe Superficies is Perennial: Thefe, agair,, have either a plain Flower, as the Ckamtedrys Vulgaris, Thucrium, and the Marum Syriacum ; or a Flower with a Lip, which they call a Lahated Flower ; or one fomething in the form of an Helmet, which they call Galeated ; as the Sacria Stuchas, Hyffopus, RofmarinuSi Satureia, Marum vulgare, T'hymum vulgar e, and the 3>c- liurn Moutanum.

z°< The Herlacee, or fuch whofe Stalks are not Peren- nial ; thefe are the Mentha, Verbena, Diffamnus Creticus t tninum, Galeopfis, Ne- peta, Setonica, 'Prunella, Stachys, Clinopodium vulgare, Lamhim, Moluca Hedera Terrejlris, Galericulata, Cala- mintba, Meliffa, Marrubitim Commune, nigrum and aquati- cum ; Cbamiepctys, Scarodonia, Scordium, Sugula, Syderi- tis, Cardiaca.

VERTICITY, is that Property of the Loadftone, where- by it turns to fome particular Point. See Magnet.

The Attraction of the Magnet was known long before its Verticity. See Compass, Needle, gJc.

VERTIGO, in Medicine, an Indifpofition of the Brain, wherein the Patient fees the Objects about him as if they turn'd round, and fancies he turns round himfelf ; tho all tha while at reft.

Phyficians diftinguiih two Kinds, or rather, two Degrees of Vertigoes : The firft, call'd a Simple Vertigo, is when the Body and external Objects appear to turn round, without any great dimnefs of Sight.

The other, call'd Scotomia, or Vertigo I'enebrofa, is when the Eyes are darken'd, and as it were cover'd with a Mift. See Scotomia.

Some make a third Stage, viz. a Vertigo Caduca, where- in the Patient actually falls down : But this feems fcarce to differ from an Epilepfy. See Epilepsy.

Sometimes the Vertigo is feated in the fore-part of the Head, and fometimes in the hind-part : whereof, the latter is much the more dangerous.

Bellini accounts for the Vertigo very well, from a preter- natural Motion in the Retina : for 'tis evident, an Object will feem to move circularly, if the Images thereof, painted on the Retina, fall fucceffively on different Parts of the Re- tina. See Retina.

This they may do, either by the Objects moving while the Eye is at reft, or from the Eye moving while the Objects reft ; or, laftly, the Object and Eye being both at reft, the Rays falling on the fame Place by the Optic Nerve's be- ing alone in Motion. For fince a right and an oblique Inci- dence do not excite the fame Tremors in the Nerves, and the fame Species of Motion ; if the Optic Nerve only be moved, and the Object be at reft, it will appear to Ihift its Situation, by the Change of Place in which it was repre- fented. See Vision.

External Caufes of Vertigines, are a continued turning round of the Body, Drunkennefs, too long Failing, immo- derate Exerciie, Surprize, Voracity, much ufe of Pulfe, O- nions, Leeks, Raddiihes, Cabbage, Muftard, $3c and in the general, whatever may prefs, diftend, or contract the Arteries.

The Word is form'd a vertendo, from turning. The firft Step in the Cure, is bleeding in the Jugular, or Cupping ; then they proceed to an Emetic ; then a Vefica- tory on the Neck, or a perpetual Blifter, or Iffues ; with Sternutatories, and the other Medicines that obtain in the Apoplexy. See Apoplexy.

VERTlLLAGE, in Agriculture, the 'tilling, or prepa- ring of Ground ro receive the Seed, by turning, ftirring, or tofling it. See Tilling. VERTUE. See Virtue. VERTUOSO. See Virtuoso.

VERU-MONTANUM, in Anatomy, a Term compound- ed of the two Latin Words, Veru, and Montanum ; fignify- ing a kind of little Valve, in the Place whete the Ejacula- tory Ducts enter the Utethra. See Valve, Urethra, (3c Its ufe is, to prevent the Urine, in paffing the Urethra, from getting in at thofe Ducts, and fo mixing with the Se- men. See Urine, £$c.

VERY Lord, and Very Tenant, are thofe that are im- mediate Lord and Tenant, to one another.

And know ye, that in taking of Lcafcs fix things

are necejfary, viz. Very Lord, and Very Tenant ; Service behind ; the Day of the taking ; Seifin of the Services, and within his Fee ; and that a Man is not Very Tenant, until he have attumed to the Lord by fome Service, Old Nat. Brev. See Tenant, SJfc-

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