Page:Cyclopaedia, Chambers - Volume 1.djvu/120

 ALT ( 73 )

61.) from which Point you had defcrib'd the Quadrantal Arch AF. Make CE equal to the Height of the Pin or Wire, and thro' E draw E D parallel to C A, and make it equal to C G, the length of the Shadow ; then will a Ru- ler, laid from C to D, interfect the Quadrant in B; and BA is the Arch of the Sun's Altitude, when mcafur'd on the Line of Chords, Sec Chord.

Suppofe, e.g. the Altitv.de he required of a Tower AB, whole Top is vifible at the Ditknce of five Miles : Then will DCB io', from whofe Secant jccooi<58, fubrracting the whole Sine 10000000 ; the Remainder A B is i<58, which will be found 351 Varis Feet.

Altitude oftheEye, in Perfpective, is a right Line let fall from the Eye, perpendicular to the geometrical Plane.

Altitude, in Aitronomy, is the Dil^ance of a Star, or other Point in the Mundane Sphere, from the Horizon. See Sphere, Horizon, Distance, $$c.

This Altitude may either be true or apparent. — If regard be had to the rational, or real Horizon ; the Altitude is laid to be trite or real : If to the apparent, or feniible Ho- rizon j the Altitude is apparent. — Or rather, the apparent Altitude is fuch as it appears to our Obfervation ; and the true, that from which the Refraction has been fubrracted. Sec True, Apparent, &c.

The Altitude of a Star, or other Point, is properly an Arch of a Vertical Circle, intercepted between the affign- ed Point and the Horizon. See Vertical. — 'Hence,

Meridian Altitude. — The Meridian being a vertical Circle ; a Meridian Altitude, that is, the Altitude of a Point in the Meridian, is an Arch of the Meridian intercep- ted between it and the Horizon. See Observation.

To obferve the Meridian Altitude of the Sim, of a Star, or other Vh&mnzenon, by means of the Quadrant, fee Me- ridian Altitude.

To obferve a Meridian Altitude by means of a Gnomon, fee Gnomon.

Altitude of the Vole. — Since the Meridian partes thro' the Poles of the World j the Altitude of the Vole, is an Arch of the Meridian, intercepted between the Pole and the Horizon.

To obferve the Altitude or Elevation of the Vole, fee E- levation, and Pole.

The Altitude of the Vole coincides with the Latitude of the Place. See Latitude.

Altitude of the Equator, is the Complement of the Altitude of the Pole to a Quadrant of a Circle. Sec Ele- vation of the Equator.

To find the Altitudes of the Sun, Stars, &c. by the Globe. See Globe.

Altitude of the Nonagefimal, is the Altitude of the 19th Degree of the Ecliptic, reckon'd from the Eall Point. See Nonagesimal.

Refraction of Altitude, is an Arch of a Vertical Circle, as S s, (Tab. Afironomy, Fig. 2.8.) whereby the Altitude SE, of a Star or other Body, is increas'd by means of the Refraction. See Refraction.

Varallax of Altitude, called alio fimply Varallax 5 is the difference CB, (Tab. Afiron. Fig. 27.) between the true and apparent Place of a Star 5 or, the Difference B C, between the true Diftance of a Star AB, and the obferved Pittance AC, from the Zenith A.

The Parallax diminifhes the Altitude of a Star, or in- creafes its Distance from the Zenith.

To find the Varallax of Altitude, &c. fee Parallax.

Altitude of a Figure, in Geometry, is the Diftance of its Vertex, from its Bafe ; or the length of a Perpendicular let fall from the Vertex to the Bub. Sec Figure, Base, and Vertex.

Thus, KM, (Tab. Geometry, Fig. 19.) being taken for the Bafe of the Rectangle-Triangle, KLM : the Perpendicu- lar K M, will be the Altitude of the Triangle.

Triangles of equal Bafes and Altitudes, are equal ; and Parallelograms, whofe Bafes and Altitudes are equal to thofe of Triangles, are juft double thereof. See Triangle, Pa- rallelogram, \3c.

Altitude of Motion, is a Term ufed by Dr. Wallis, for the Meafure of any Motion, eitimated according to the Line of Direction of the moving Force. See Motion.

ALTO €J? Sajfi, or in Alto & in Sap, in Law, figni- fies the ablblute Reference of all Differences, fmall and great, high and low, to fome Arbitrator Qr indifferent Per-

fon.- Vateat univerfis per pnefentes quodWdlielmus Ty-

lar de Tetton, & T'homas Go-zvcr de Almefire, pofuernnt fe in Alto $$ in Safib, in arbitrio quatuor Hominum, viz. — de quadam querela pendente inter cos in curia. Nos & terrain no fir am Alt'e ££? Safse ipfius domini Regis fuppofuimus vo- luntati. Du Cange.

ALUDELS, in Chymiltry, Subliming-Vots. See Subli- mation.

Atudels, are a Range of earthen Tubes, or Pots without bottoms ; fitted, one over another, and diminifhing as they advance towards the Top. — The loweft is adapted to a Pot,

A M A

placed in the Furnace, wherein the Matter to be' fublimed is lodg d.— And at the Top is a Head, to retain the Flow- ers which afcend. See Flower.

ALVEAR1TJM, in Anatomy, the bottom of the Con cha.or hollow ot the Auricle. See Auricle, and Concha

The Alveariiim Auricula terminates at the Meatus Au- ditorius. See Meatus.

The Word literally Signifies See-hive, form'd of Ahem Channel.

ALVEOLI, in Anatomy, little Sockets in the Jaws wherein the Teeth are fet. See Teeth, and Jaw.

The Alveoli are lined with a Membrane of exquisite Senfe, which feems to be nervous, and is wrapt about the Roots of each Tooth ; from whence, and the Nerve, proceeds that Pain called Odmtalgy, or Tooth-ach. See Odontalgy, and

ToOTH-ACH.

ALV1DUCA, a Term ufed by fome Writers for hofen- ing Medicines. See Purgative, lie.

The Word is compounded of Alvus, and duco, I draw.

ALUM, Alumen. See Alluii.

ALVUS, among Anatomists, is iomctimes ufed to exprefs the inteflinal Tube, from the Stomach to the Aims. See In- testines.

Alvus, in a Medicinal Senfe, is taken for the State, and Condition of the Pieces, or Excrements contain'd within that Cavity. See Excrement, iSc.

Thus, when a Pcrfon is laxative, it is called Alvus li- quid?. ; and when coftive, Alvus adftriBa. See Costive, Laxative, £yc:

AMABYR, or Amvabyr, in our antient Law-Books. — ■ Pretium virginitatis domino folvendum. — 'Paella dicitur ejje defertum Regis, e? cb hoc Regis eft de ea Amvabyr habere.

The Cuftom was in honour of Clun, and obtained till fuch time as Henry Eatl of Arundel, 7emp. Phil, e? Mar. in consideration of 60 1, releafed it to all his Tenants thete, by the Name of the Cuftom of Amabyr and Chevage. See Chevage.

AMAIN, a Sea Term, ufed by a Man of War, to his Enemy ; and Signifying, yield. — Hence, yi ftrike Amain, that is, to lower your Topfails.

AMALGAM, or Amalgama, in Chvmillry, a Mai's of Mercury, united and incorporated with a Metal. See Mer- cury, and Metal.

The Amalgam of Mercury with Lead, is a foft, friable Substance, of a Silver Colour. See Lead.

By warning and grinding this Amalgam with fair warm Water in a glafs Mortar, the Impurities of the Metal will mix with the Water; and by changing the Water, and re- peating the Lotion again and again, the Metal will be fur- ther and further purified. — Soerhaave mentions it as one of the greateft Secrets in Chymiltry, to contrive to bring oft" the Liquor at laft as clear and unfully'd as when firft pour'd on the Amalgam ; which might afford a Method of making the nobler Metals, or procuring them from the Bafer. See Transmutation, Philosopher's Stone, &c.

This philofophical way of purifying Metals, may be ap- plied to all the Metals, except Iron and Copper. See A- malgamation.

The Word Amalgama is form'd of the Greek ay-a, Jimul, together, and ytqt&y, ]ungere, to join.

AMALGAMATION; in Chymiflry, the Operation of making an Amalgama ; /'. e. of calcining, or rathet diflbl- ving fome Metal, efpeciaily Gold, by means of Mercury.

See A.MALGAMA.

Amalgamation is performed by fufing, or at leaf! igniting the Metal ; and in this State adding a proportion of Mer- cury thereto ; upon which they mutually attract, and incor- porate with each other. See Mercury.

All Metals, except lion and Copper, unite and amalga- mate with Mercury ; but Gold with the greateft facility ; Silver the next ; then Lead, and Tin. See Metal, S?c.

The Amalgamation of Gold is usually perform 'd by heat- ing the Lamina; or Plates of Metal red hot; after which. Quicksilver is to be pour'd upon 'em, and the Mixture ftirr'd with a little Iron Rod, till it begins to rife into Smoke. — It is then thrown into a VeSTel full of Water, where it coagu- lates and becomes manageable.

This Calcination is in great ufe among Goldfmiths, and Gilders, who by this means render Gold fluid and ductile for their Purpofes. — .Such Mixture or Amalgama being laid on any othet Metal, for inftance, Copper ; and this after- wards placed on the Fite to evaporate; the Gold will be left alone on the Surface of the Copper 1 which makes what we call Gilding. See Gilding.

The Blacknefs adhering to the Amalgama may be waffled away with Water ; and a deal of the Mercury prefs'd out thro' a linen Cloth : The reft being evaporated in a Crucible, the Gold remains behind in an impalpable Pouder. See Gold.

Gold retains about thrice its own weight of Mercury. This Operation is denoted among Chymifts by the Lettets AAA. See Character.

U AMA-