Page:Cyclopaedia, Chambers - Volume 1.djvu/193

 ASC

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ASC

This is otherwife called the northern Node, and repre- fented by this Character £>,. See Node, &q.

Ascendinc, Afcendens, in Matters of Genealogy, &c. See Ascendent.

Ascending Signs, among Aflrologers, arc thofe which are upon their Afcent or Rife; from the Nadir or loweft Part of the Heavens, to the Zenith or higheft. See Sign, Zenith, Nadir, &c*

Ascending, in Anatomy, is applied to fuch Veffels as carry the Blood upwards, or from lower to higher Parts of the Body. See Blood and Vessel.

The Afiending Aorta, Aorta afcendens, is the fuperior Trunk of the Artery, which furnifhes the Head. See Aorta.

The afiending Cava, Vena Cava Afcendens, is a large Vein form'd by a Meeting or Union of. the two lliacks of one Side, with thofe of the other. See Cava.

Many of the antient Anatomifts, call*d this the defcending Cava ; as imagining that the Blood defcended from the Li- ver by this Vein, to fupply the Parts below the Diaphragm. But the Moderns have fhewn that it has a quite contrary life, and ferves for the Conveyance of the Blood from the lower Parts to the Head; whence its Appellation Ascen- dent.

ASCENSION, Ascensto, a rifing, or moving upwards. See Ascent, Ascendant, Ascending, ££c. v

Ascension is particularly ufed for that miraculous Ele- vation of our Saviour, when he mounted to Heaven in the Sight of his Apoftles. —

Hence alfo, Ascension-®^', a Feftival of the Church, held ten Days before Whitjontide, in Memoty of our Sa- viour's Afienfion. See Feast. - Ascension, in Aftronomy, is either right or oblique.

Right Ascension. See Right Afienfion.

To find the Right Afcenfions of the Sun, Stars, &c, tri- gonometrically, fay, as Radius is to the Cofine of the Sun's greater!: Declination, fo is the Tangent of the Diftance from Alries or Libra, to the Tangent of Right- Afienfion.

To find the Right-Afcenfions mechanically by the Globe. See Globe.

The Arch of Right- Afienfion, is that Portion of the Equa- tor intercepted between the beginning of Aries, and the Point of the Equator which is in the Meridian : Or it is the Number or Degrees contained therein. — This coincides with the Right- Afienfion it felf. — The Right- Afienfion is the fame in all Parts of the Globe.

We fomctimes alfo fay, the Right- Afienfion of a Point of the Ecliptic, or any other Point of the Heavens. See Descension.

Oblique Ascension. See Oblique Afienfion.

To find the Oblique Afcenfions of the Sun, either trigo- nometrically, or by the Globe. See Ascensional "Diffe- rence, and Globe.

• 'the Arch of Oblique- Afienfion, is an Arch of the Hori- zon intercepted between the beginning of Aries, and the Point of the Equator which rifes with a Star or Planet in an Oblique Sphere.— This coincides with the Oblique Aj- cenfion it felf. — The Oblique Afcenfions change according to the Latitude of the Places.

The Difference between the Right and Oblique Afcen- fions, is called the afccnfional ^Difference. See Ascen- sional.

Ascensional Difference, is the Difference between the Right and Oblique ,-fienfion. See Ascension.

Or it is the Space of Time which the Sun rifes or fets before or after fix of the Clock.

To find the Afienfional Difference trigonometrically, ha- ving the Latitude of the Place, and the Sun's Declination given; fay, As the Co-Tangent of the Latitude, is to the Tangent of the Sun's Declination, fo is the Radius to the Sine of the Afienfional Difference.

For Example, fuppofe the Latitude be 51. 30'. and the Sun's Declination 9. 00'.

Then, to the Ar-co. of the Co-7 Tangent of - _ _ ... ./, 5 1 • S°\ °.°5>5>395 Add the Tangent of — -— 9. 00. 9,199712.

Sum is the Sine of — —. n°. 29' =9, 299107

which is the afienfional Difference required; and being re- duced into Time, by allowing four Minutes of an Hour for every Degree, it will be 44.'. 29". See Time.

If the Sun be in any of the northern Signs, and the af- ccnfional Difference, as D O, be fubftracled from the Right Afienfion D, in Tab. Aftronomy, Fig. 63, the Remainder will be the Oblique Ajcenfion O.— If he be in a fouthern Sign, the afienfional Difference being added to the Right Afcenficn, the Sum is the Oblique Afienfion ; and thus may Tables of Oblique Afcenfions be confiru&ed for the feveral Degrees of the Ecliptick, under the feveral Elevations of the Pole. See Table. ■

ASCENSORIUM occurs in our antient Writers for a Stair or Step. See Stair.

ASCENT, Ascensus, the Motion of a Body tending from below upwards. See Motion-

In this Senfe the Word Hands oppofed to Defcent. See Descent.

The Peripateticks attribute thefpontaneous 3$eHt "of Bo- dies, to a Principle of Levity inherent in them. See Levity.

The Moderns deny any iiich Thing as lpontaneous Levity, and fhew that whateverafcends, docs it in virtue offome ex- ternal ImpulfeorExtrufior. Thus it is that Smoak, and other rare Bodies, afcend in Atmofphere ; and Oil, light Woods, e^c. in Water: Not by any external Principle of Levity, but by the fuperior Gravity or Tendency downwards of the Parts of the Medium wherein they arc. See Gravity, Medium, Atmosphere, £5?c. I

The Afient of light Bodies in heavy Mediums is pro- duced after the fame manner as the Afient of the lighter Scale of a Ballance. — It is not that fuch Scale has an inter- nal Principle whereby it immediately tends upwards- but it is impelled upwards by the Prieponderancy of the other Scale ; the Excefs of the Weight of the one having the fame EfFecT: by augmenting its Impetus downwards, as fo much real Levity in the other : By reafon the Tendencies mutually oppofe each other.- — See this further iliuftrated under the Articles Specific Gravity, Fluids, HydrostaticalS 1 ^/- lance, &c.

Ascent of Bodies on inclined Planes. See the Doctrine and Laws thereof, under the Article Inclined Plane.

Ascent of Fluids, is particularly underftood of their ri- fing above their own Level between the Surfaces of nearly contiguous Bodies, or in flender capillary Glafs Tubes, or in Veffels filled with Sand, Afhes, or the like porous Sub- fiance. See Fluid.

This EfFecT: happens as well in vacuo as in the open Air, and in crooked as well as ftrait Tubes. — Some Li- quors, as Spirit of Wine, and Oil of Turpentine, afcend fwifter than others ; and fome ri r e after a different manner from' others. Mercury does not afcend at all, but rather fub fides.

The Phenomenon, with its Caufes, &c. in the Infiance of Capillary Tubes, will be fpoke of more at large under the Article Capillary Tube.

As to Planes — Two fmooth polifhed Plates of Glafs, Me- tal, Stone, or other Matter, being fo difpofed as to be al- moft contiguous, have the EfFecT: of feveral parallel capil- lary Tubes ; and the Fluid rifes in them accordingly, the like may be faid of a Veffel fill'd with Sand,(£?r. the divers little Interfaces whereof form, as it were, a kind of Ca- pillary Tubes. So that the fame Principle accounts for the Appearance in them all. And to the fame may probably be afcribed the Afient of the Sap in Vegetables.' See Ve- getable and Vegetation.

Thus Sir /. Newton—' If a large Pipe of Glafs be filled 1 with lifted Afhes well preffed together, and one End dip- ' ped into flagnant Water, the Fluid will afcend flowly in ' the Afhes, fo as in the Space of a Week or Fortnight, to ' reach the Height of 30 or 40 Inches above the fiagnant 1 Water. This Afient is wholly owing to the Action of ' thofe Particles of the Afhes which are upon the Surface of ( the elevated Water ; thofe within the Water attracting as

' of fuch Particles is very ftrong; tho' being lefs denfe and
 * much downwards as upwards : It follows, that the Action

' Glafs, which keeps Quickfilver fufpended to the Height ' of do or 70 Inches, and therefore acls with a Force which 1 would keep Water fufpended to the Height of above 60 4 Feet. — By the fame Principle, a Sponge fucks in Water,
 * clofe than thofe of Glafs, their Action is not equal to that of


 * and the Glands in the Bodies of Annuals, according to

1 Juices from the Blood.' Opticks, p. 367.
 * their feveral Natures and Difpofitions, imbibe various

If a Drop of Oil, Water, or other Fluid, be laid on a Glafs Plane perpendicular to the Horizon, fo as to fiand without breaking or running off; and another Plane inclin- ed to the former, fo as to meet a-top, be brought to touch the Drop ; then will the Drop break, and afcend towards the touching End of the Planes : And it will afcend the fa- tter in proportion as it is higher, by reafon the Diftance be- tween the Planes is conftanrly diminiiliing.— Afrer the fame manner, the Drop may be brought to any part of the Planes, either upward or downward, or fideways, by altering the Angle of Inclination.

Laftly, if the fame perpendicular Planes be fo placed, as that two of their Sides meet and form a fmall An^le, 'the other two being only kept a-part by the Interpolation of fome thin Body 5 and thus immcrged in a Fluid tinged with fome Colour: The Fluid' will afcend between the Planes and this the higheft where the Planes are neareft 5 fo as to* form a Curve Line, which is found to be a juft Hyperbola, one of the Afymprotes whereof, is the Line of the Fluid!

the other being a Line drawn along the touching Sides.

The