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cate and moiflien the Heartj and prevent any Inflammation that
might probably arife from the dry Fridfion. of the Heart and
its Caplula. But this latter Ufe is controverted ; for fome take
the Humour found in it to be unnatural and will have it
forcibly Separated by the convulfive Agonies Supervening in
the Article of Death. In effe6I, Anatomifis are puzzled to
find whence it lhou'd come, or from what Veffels it is fecreted.
The word Tjericardium is form'd from the Greek wrepi
about and capiJict Heart.
Dr. Jeil, in his Treatife of Anim. Secretion Ihews that the
Liquor in the Pericardium mult be the moft Fluid of any
feparated from the Blood, becaufe its Particles unite fir f,
and are fecreted firfi. For thofe Particles which unite firfi,
will have the greatel attraffive Force, confequently their Par-
ticles mult be the mofi Spherical and moff Solid; and there-
fore their Conta4S the leafi of any, therefore the mofi Fluid.
See FLUIDITY.
In the Memoirs of the French Academy, M. de     Mortal
gives an Infiance of a Pericardium, which being open'd, the
Liquor contain'd therein, was found congeal'd into a Confif-
tence fit to be cut with a Knife, and two fquare Fingers
thick about the Heart.
PERICARPIA, from      £spt, circum, about, and Carpus
the Wriff, are Medicines that are applied to the Wrift.
PERl CARPUS, in Botany, a Pellicle, or thin Mem-
brane, incompalfing the Fruit or Grain of a Plant. See
FRUIT, SEED, e5c.
The Wordis form'd of the Greek 7sp; about and xcpwsa Fruit.
PERICHORUS, in Antiquity, a Name given by the
Greeks,to their profane Games and Combats i l. e. to fuch as
were not confecrated to any of the Gods. See GAMES.
The Word in the Original, fignifies near or neighbouring;
apparently, becaufe none but the People of the Neighbour-
hood attended at thefe obfcure Exercifes.
The Cha    'pions did not fight in Honour of any God or
fleroe, as in the othersx but only for the prize Sake.
The Word is form'd from the Greek %spi about and x4'
Country.
PERI CRANIUM, in Anatomy, a thick folid Coat or
Membrane, covering the out Side of the Cranium or Skull.
See CRANIUM.
Some call it by the general Name of Periofteum, becaufe of
its adhering to the Bone: others divide it into two Mem-
branes, the under whereofirnmediately inverting the Skull, they
call Periofleum ; and the upper the Pericranium. But in effect,
'tis but one double Membrane, confifting, as moff others do
of two Coats. 'Tis fuppofed to have its Origin from the dura
Mater; which palling thro' the Sutures of the Skull, by
means of feveral Filaments forms this thick Membrane: At
leaf, 'tis {ill found conneaed to the dura Mater by Fi-
bres tranfmitted from it to the Membrane, thro' the Sutures.
About the Origin of the temporal Mufcles, the two Coats of
the Tericranium part; the Outer paffing over thofe Mufcles,
and the Inner Rill adhering clofe to the Cranium. See PE.-
PuOSTEUM.
The Word is form'd from the Greek mps' about and xparla
Head.
PERIDROME, PERIDROMUS, in the ancient Archi-
teaure, the Space, Gallery, Alley, or the like, in a Peripte-
re, between the Columns and the Wall. Salmaftus obferves
that the Peridromnes ferved for Walks among the Greeks.
PERIOECI, in Geography, fuch Inhabitants of the Globe
as have the fame Latitudes, but opofite Longitudes; or live
under the fame Parallel, and the fame Meridian, but in dif-
ferent Semi-circles of that Meridian. See GLOBE.
Thefe have the fame common Seafons throughout the
Year; and the fame Phmnomena of the heavenly Bodies; but
their Hours, or times of the Day, are oppofite to each other.
When v. g. with the one 'tis Mid-day; with the other 'tis
Mid-night. See DAY and SEASON.
The Word is form'd from the Greek wepi about and oixie
I inhabit.
PERIEGETES, a Greek Term, fignifying a Perfon who
conduas another about a Thing, to Ihow it him, e.c.
It is applied in Antiquity to Geographers; efpecially to
thofe who defcribed the Sea-Coafis: Thus WDionyfus is filed
!Periegetes, for publifhing a Geography in Hexameter Verfes;
which Eiftathius has commented on, both, in Greek.
The Name Periegetes was alfo given to thofe who con-
Auaed Strangers about in Cities, to Ihew 'em the Antiqui-
ties, Monuments, Curiofities, Wc. thereof.
Thefe Periegetes were the fame with what they now call
Antiquaries inItaly. SeeANTI0UARY.
P ERIGJEUM, PERIGEE, in Afironomy, that point of
the Heavens, wherein the Sun and Planets are at their leaft
Diffancefrom the Earth. See EXCENTRIC.
The Moon in her Perigee is 5 3 or 54 Semi-dameters of the
Earth diflant from us. See MOON.
The Term is but little ufed, except in the Ptolomaic
Syflem; where the Earth is placed in the Centre of the
World, and the Difiances of the Planets chiefly confider'd
with regard thereto- being form'd of the Greek Aepi, about
and -ad Srerra, Earth.


P E R


The Copernicans ufe the Word Peribeliam in lieu.
rigeum5; becaufe they place the Sun in the Centre. (
RIIELIUM.
PERIHEILIUM, in Afronomy, that point of the
of a Planet, or Comet, wherein it is at its leaft [
from the Sun. See PLANET, COMET, SON, ec.
The Word is form'd from the Greek sfri, and
SolI Sun.
The ancient Aftronomers, in lieu hereof ufed Peri
becaufe they placed the Earth in the Centre. See
GIEUM.
- PEREGRINARY, PEREGRINARIUS,in the
Monafteries, a Monk to whom was committed the
receiving, and entertaining Strangers, or Vifitors.
PERIMETER, in Geometry, the Ambir, or exte
bounds a Figure or Body. See FIGURE.
The Perimeters of Surfaces, or Figures, are Lines; i
Bodies are Surfaces. See SUPERPICIBS.
In circular Figures, Wc. inflead of Perimeter we f
cumference or Periphery. See PERIPHiE{ERY.
The Word is form'd from the Greek Eit and yiTf
fure.
PERINEUM, in Anatomy, the Space between X
nis or Scrotum, and the Fundament; properly the Li
tous Seam ; call'd by the Latins, Famen, and Interefen
The Word Perinf'um is form'd from the Oreek
vghcewv to inhabit.
PERINDE Valere, in the Canon Law, a Difp
granted a Clerk, who being legally incapable of a I
or other ecclefiaflical Fundion, is, dejadfo, admitte
See DISPENSATION.
The Perinde Valere, is a kind of Writ; thus call
two Words therein, fignifying the Difpenfation to be
lent or tantamount to a legal Capacity.
PERIOCHA, an Argument containing the Sum o
courfe.
PERIOD, in Afironomy, the Time taken up by a
Planet, in making a Revolution; or the Duratior:
Courfe, till it return to the fame Point of the Heaven
REVOLUTION.
The Su's or rahe th ..at      .er.o, . 36 Das fiv


The Sun's, or father the Earth's 'Period, is 365 Days, five
Hours, 4.; Min. That ofthe Moon 27 Days, 13 Hours, 9 Min.
&)c. See SuN, MOON, Ujc.
The Periods of the Comets are now many of 'em pretty
well afcertain'd. See COMET.
There is a wonderful Harmony between the Difilances of the
Planets from the Sun, and their Periods round him; the
great Law whereof is, that the Squares of the Periodic Mimes
are ever proportional to the Cubes of their mean Dijfances froxn
the Sui. See PLANET.
The feveral Pericds and mean Diflances of the feveral
Planets are as follow.


PERIODS.
Days   h.          mean Dil
Saturn   105 79  6   36  26  953800
Jutpiter  4332  12  20   35  520110
Mars       686  23  27   30  152369
Earth      365   6   9   30  I00000
Ve'nus     224  I6  49   24   72333
Mercury     87  23  15   53   38710


* PERIOD, in Chronology, an Epocha or interval of I
by which the Years are accounted; or a Series of I
whereby, in different Nations, and on different Occ,
Time is meafur'd. See TIME.
Such are the Callipic, and Metonic Periods, two dig
Correfions of the Greek Calendar; the 7lian PerioA
vented by 7of Scaliger; the Vilorian Period, Wc.
Metonic PERIOD, or Cycle, call'd alfo the Cycle of
Moon, is a Series of I 9 Years, which elaps'd the new an(
Moons, are fuppofed to return to the fame Day of the
Year: It was thus call'd from its Inventor Meton. See
TONIC. See alfo CYCLE.
Callipic PERIOD, is a Series of 76 Years, returning
perpetual Circle; which elaps'd the new and full Moons&
fuppofed to return to the fame Day of the folar Year.
Co/Jipic Period is an improvement on the Metonic of 19 I
which proving inaccurate, Calitp us the Athenian multi
it by 4, and thus arofe the Caliptic Period. See CALIPI]
Ifipparchus's PERIOD, is a Series of 304 folar Year;
turning in a conflant round; and refloring the new an(
Moons to the fame Day of the folar Year; according t
Sentiment of Hipparchus.
This Period arifes by multiplying the Calippic Period
mipparchus afiumed the Quantity of the folar Year
365 Days, 5 Hours, 55 xiz". And hence concluded th
104 Years, Callippus's Period wou'd Err a whole Day.
therefore multiplied the Period by 4, and from the Pro'
capt away an entire Day. But even this does not refpor
new and full Moons to the fexe Day throughout the v
p


P ER