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Oblique DES ENSION, is a Point, or Arch of the Equator,i
Which defcends at the fame TUne with a Star, or Sign be-
low the Horizon, in an oblique Sphere.    See oblique
SPHERE.
Defcenfions, both Right, and Oblique, are accousted
from the frfiPoint of,4ries, or the Vernal Interfeaion; ac-
cording to the Order of the Signs ; that is, from WeQc to Eafi.
And as they are unequal, when it happens that they aknfwer
to equal Arches of the Ecliptick, as e. gr. to the Iz Signs
of the Zodikck, it follows, that Sometimes a greater Part of
the Equator rifes, or defcends with a Sign, in which Cafe the
Sign is faid to afcend, or defcend rightly: , And fometimes
afain a lefs Part of the Equator rifes, or fets with 'the fame
Sign, in which Cafe it is raid to afcend, and defcend ob-
liquely. See ASCENSION.
eRefraafion of the DESCENSION, S'c.  See REFRAC-
TION.
DESCENSIONATL ZDifference, is the Diference be-
tween the Right, and Oblique DefcenJion of the fame
Star, &c. See DIFFERENCE.
DESCENT, or DISCENT, in Law, an Order, or Man-
ner wherein Lands and Tenements are derived to any Man
from his Anceflors.
Thus, to make his Defcent from his Anceflors, is to mhew
how, and by what particular Degrees, the Land in Queflion
came to him from his Anceftors.
EDefcent is either Lineal, or Collateral.
Lineal DESCENT, is that convey'd down in a right Line
from the Grand-Father to the Father, and from the Father
to the Son, from the Son to the Grand-Son, Wc.
Collateral DESCENT, is that fpringing out of the Side
of the Line, or Blood, as from a Man to his Brother, Ne-
phew, or the like.  See COLLATERAL, and DEGREE.
If one dies feifed of Land, wherein another has Right to
enter, and it defcends to hisHeir, fuch!Defcent mhall take
away the other's Right of Entry, and put him to his Adfion
forRecovery thereof  Stat. 31. len. III.,
DESCENT'S, in Genealogy, and Heraldry, the Order, or
Succeffion of Defcendants in a Line, or Family. See DE-
SCENDANT.
One Dl~efcent, two  efcents, &c.  A Gentleman is of
perfed Blood, who has four !Defcents of Gentility, both by
his Father, and Mother's Side, i.e. whofe Great-Grand-
Father, Grand-Father, and Father, on both Sides, were
all Gentlemen. See GENTLEMAN.
DESCENT, is alfo ufed in Heraldry, to exprefs the
coming down of any Thing from above.
Thus a Lyon en Defcent, is a Lion with his Head to one
of the bafe Points, and his Heels towards one of the Corners
of the Chief; as if he were leaping from fome high Place.
DESCENT, Fall, in Mechanicks, Ec. is the Motion, or
Tendency of a Body towards the Center of the Earth, either
diretly, or obliquely. See CENTER, and MOTION.
It is to be here obferv'd, Firfl, That a Body cannot de-
fcelld, unlefs it can divide, and feparate the Medium;
which it cannot do, unlefs it be fpeciflcally heavier than the
Medizrn.   For fince Bodies cannot penetrate each other,
one muff give Way 'ere the other can move: And again,
Tho' a Mediu, e. gr. Water be di vifible, yet if it be fIeci-
fically heavier than another, e. gr. Wood, it is only heavier
as it contains more Particles of Matter in the fame Bulk;
all which have an Impulfe downwards, and consequently
in Water there is a greater Impulfe than in the fame Bulk
of Wood. See SPECIFIC Gravity.
Secondly, The Dieficending Body lofes as much of its
Weight, as is the Weight of the Medium, with the Force of
its Cohefion. See MEDIUM.
Thirdly, The lefs the Bulk of the EDefcending Body is,
the more of its Gravity does it lofe in the fame Medium.
For tho' the Proportion of the fpecific Gravity of the one to
the other be fill the fame in a greater, or lefs Bulk, yet the
lefs the Body, the more the Surface, in Proportion to the
Mafs *  and the more the Surface, the more the Friaion, or
Refifance. See FRICTION, and RESISTANCE.
The Caufe of this Defcent, or Tendency downwards, has
been greatly controverted. There are two oppolite HfYpo-
ithefes advanced; the one holding it to proceed froman in-
ternal, and the other from an external Principle. The firil
maintained by the Peripateticks, and Fpicureans, and New-
toniays; and the latter by the Carteftans, and Ga endifis.
The Peripateticks teach, that heavy Bodies fall by cer-
tain motive Powers, flowing from their Forms towards the
Centre of the Earth, as their proper Element, or Place in
the Univerfie. Thefe Powers they call mpetus's; and will
have them to have been imprefs'd on the feveral Parts of the
Earth, at the 'Creation; being a Tendency of the Parts to
the whole. And they fuppofe, that it is by means hereof, that
the whole is fill preferved in its Integral State. Adding,
that if there were a perfe& Vacuity in any Part of the
Air round us, a Stone placed therein would not at all fall,
or tend towards the Earth,' as being no longer a Part there-
of, nor having the natural Impetus.


D) E s


The ancient Epicu9reans, or -tomils, *i te   i j
Newtonian Philofophers, hold, that a    B rdies Ip
tend downwards, and that the more                orronly as te c n
tain the more Matter; conf.quently perfely OId Boi
fuch as they fuppofe Atoms, or primitive CorpufcleeF
the moi of all. See GRAVITY.
The Cartefians afcribe the Caufe Of:Defcent Of Bies
a circular Motion of the -iEther, which they feign for
very Purpofe. According to them, all circular Motion is un
natural; and therefore is continually endeavouring to recede
from its Center, and to change into a Refi-linear Motion
confequently fuch as have the moreIMtion, recede toh  o
and in receding, deprefs, or thrufi down fuch asI vefs
Motion.   And thus the Air being moved with -te snof
vehement Velocity, recedes more than folid Bodies, and' b
that means drives them towards the Center.       + y
The Gaendzfts account for the Dejfcent of heavy Bodies
by fuppofing certain magnetick Rays proceeding out of the
Earth, and confiing of contiguous Particles, which by their
continual Emiffion retain the Rigidity ofRods, or firetchdd
Cords.  Thefe Rays being di fufed every way from the
Earth, as a Center, firike, or impinge on what iolid Bodies
they meet withal in their Progrefs, and penetrate the fame,
fome direcaly, and others obliquely, and refraatedly, after
the Manner of Rays of Light. Thefe Rays, fay they, are
a Kind of Arms i and the Defefions, and Curvatures of
their Extreams, as it were Fingers, orHooks, which pull,
or draw Bodies from above towards the Earth. And they
add, that thefe Rays being the more rare, as they are
more remote from the Center; their Effecl is the more feeble -
and the fDefcent of Bodies is the more flow, in Proportion
as they are higher.
Laws of the DESCENT of B'odies.
I. Heavy Bodies in an unreliiing Medium fall with.
an uniformly accelerated Motion. See the Laws of uni-
formly accelerated Motion under the Articles ACCELERA-
TION, and MOTION.
Hence, i. The Spaces defcended are in duplicate Ratio of
the Times, and Velocities; and increafe according to the un-
even Numbeiis -, 3, 5, 7, 9, Uc.  2. The Times, and.Ve-
locities, are in a fubcduplicate Ratio of the Spaces. 3. The
Velocities of defending Bodies, are proportionate to the
Times from the Beginning of their Falls.  4. The Spaces
described by a falling Body, are as the Squares ofthefimes
from the Beginning of the Fall.
A Body fpecifically heavier depends in a fluid Medium;
fpecifically lighter, (e.gr. the Air,) with a Force equal to the
Excefs of the Weight of the Body above an equal Bulk of
the M4fedium. For a Body only defcends in a Medium with
the Force remaining, after a Part has been fpent in over-
coming the Refiflance of the Mfedium. And this Refiflance
is equal to the Weight of an equal Bulk of the Medium:
Conlequently the Body only falls with the Excefs of its
Weight above that of an equal Bulk of the Medium.
Hence, the Power that fuflains a Body in a fpecifical-
ly lighter Medium, is equal to the Excefs of the ab-
folute Weight of the Body above an equal Bulk of the
Medium.   Thus 473 Pound of Copper in Water lofe 51
of their Weight. A Power, therefore, of 42 Pounds is able
to fufiain them.
In fuppofing heavy Bodies to defpend in an unrefifling Me-
diumr,, we conceive them free of all external Impediments,
from what Caufe foever. So that we even fet a-fide that ob-
lique Imfulfe given to Bodies while in falling, by the Rota-
tion of the Earth, tho' this produce no fenfible Irregularity
in a little Diftance.
Galliieus, who firfi difcover'd the Law of the D!efent
of heavy Bodies by Reafoning, afterwards confirm'd the fame
by Experiments; the Refult of which, repeated an hundred
times over, was, that the Zdeficet was as the Square of the
Times.
Grimaldo and Ricciolus made Experiments to the fame
Effe&, tho' in a different Manner, by letting fall a Numbec
of Balls, weighing 8 Ounces a Piece, from the Tops of fe-
veral Towers, an meafuring the Times of fadling by a Pen-
dulum. Thefe Experiments are exhibited in the fqllowing
Table.
Vibrations of   Time.     pace at the Spacedef
the Pendu-                nof the     d     ch
lum.    t           I   Time.        Time.T
.___I________        Rorn. Foot. Et m. bot.
.     5              50       10          1
10       I      40       40
15      2       30       90          50
20       3      20      I6O          70f
2S.5    4       IO      25           9f 0
6       I    -       O        15
Il      2        0       6   0       45
18       3       0      135          75
_24       4        0      _ 40 9