F O R 
P05 
P o s 
4S7 
and printed many books ; hence the name of 
Port-royalists was given to all their party, and 
their books were called books of Port-royal ; 
hence we say the writers of Port-royal, 
messieurs de Port-royal, and the translations 
and grammars of Port-royal. 
PORTA, or vena porta. See Anatomy. 
PORTERAGE. By stat. 39 Geo. 111. c. 
58, no inn-keeper, warehouse-keeper, or other 
person, to whom any box, basket, package, 
parcel, truss, game, or other thing whatso- 
ever, not exceeding lifty-six pounds weight, 
or any porter or other person employed by 
such inn-keeper, warehouse-keeper, or other 
person, in porterage, or delivery of any such 
box, parcel, & c. within the cities of London, 
Westminster, or borough of Southwark, and 
their respective suburbs, and other parts con- 
tiguous, not exceeding half a mile from the 
end of the carriage-pavement, in the several 
streets and places within the aboveinentioned 
limits, shall ask or demand, or receive or take, 
in respect of such porterage or delivery, any 
greater rate or price than as follows: 
Not exceeding a quarter of a mile 3d. 
half a mile Ad. 
■ one mile 6d. 
one mile and a half 8 d. 
• ■ two miles 1 0 d. 
For every further distance, not exceeding 
half a mile, three-pence additional. 
Persons asking or receiving more than the 
above rates, shall for every such offence, for- 
feit a sum not exceeding 20s'. nor less than 
<5«y. 
PORTICO. See Architecture. 
PORTLAND stone is a dull whitish 
species much used in buildings about Lon- 
don. It is composed of a coarse grit, ce- 
mented together by an earthy spar. It will 
not strike tire with steel, but makes a violent 
effervescence with nitric acid. See Free- 
stone. 
PORTLANDIA, a genus of the monogy- 
nia order, in the pentandria class of plants, 
and in the natural method ranking with those 
of which the order is doubtful. The corolla 
is elevated and funnel-shaped ; the anthers 
are longitudinal ; the capsule pentagonal, 
and reluse at top, bilocular, and crowned 
with a pentaphyllous calyx. There are four 
species. The grandiilora has been particularly 
described by Dr. Browne, who has also given 
a good figure of it. It has frequently flowered 
in the royal garden at Kew, and in Dr. Pit- 
cairn’s at Islington. The external bark is 
remarkably rough, furrowed, and thick : it 
has no taste. The inner bark is very thin, 
and of a dark-brown colour. Its taste is bitter 
and astringent, and its virtues are the same as 
those of the Jesuits’ bark. Infused in spirits 
or wine with a little orange-peel, it makes an 
excellent stomachic tincture. 
PORTRAIT. See Painting. 
PORTULACA, purslane, a genus of the 
monogynia order, in the dodecandria class of 
plants, and in the natural method ranking 
under the 13th order, succulents. The co- 
rolla is pentapetalous ; the calyx bifid ; the 
capsule unilocular, and cut round. r l here 
are 12 species, but the two following are the 
most remarkable : 1. The oleracea, annual, 
or common culinary purslane. There are 
two varieties ; one with deep-green leaves, 
the other with yellow leaves ; both of which 
rise from the same seed. 2. The anacamp- 
seros, perennial, or shrubby Cape purslane. 
Both these plants are of a succulent nature : 
the first is an herbaceous annual, for culinary 
uses.; and the second a shrubby perennial, 
raised by the curious for variety. They are 
both exotics of a tender quality, of the tem- 
perature of greenhouse or stove plants, The 
common culinary purslane is raised annually 
from seed for summer use, and is an excellent 
ingredient in summer salads, but improper 
for winter on account of its cold moist nature. 
The plant being tender, must be raised either 
on a hotbed or in a warm border. 
PORTU LAC ARIA, a genus of the class 
and order pentandria trig} nia. The calyx is 
two-leaved ; the petals five ; seed one, three- 
sided and winged. There is one species, 
called purslane-tree, * 
POSITION. See Architecture. 
Position, or the rule of false position, 
otherwise called the rule of falsehood, in 
arithmetic, is a rule so called, because in cal- 
culating on several false numbers taken at 
random, as if they were the true ones, and 
from the differences found therein, the num- 
ber sought is determined. This rule is either 
single or double. Single position is when 
there happens in the proposition some par- 
tition of numbers into parts proportional, in 
which case the question may be resolved at 
one operation, by this rule : Imagine a num- 
ber at pleasure, and work therewith accord- 
ing to the tenor of the question, as if it were 
the true number ; and what proportion there 
is between the false conclusion and the false 
proportion, such proportion the given num- 
ber has to the number sought. 
Therefore the number found by argumen- 
tation,’ shall be the first term of the rule of 
three; the second number supposed, the se- 
cond term ; and the given number, the third. 
See Arithmetic. Or the result is to be 
regulated by this proportion, viz. As the 
total arising from the error, to the true, total, 
so is the supposed part, to the true one. Ex- 
ample: A, 15, and C, designing to buy a quan- 
tity of lead to the value of 140/. agree that B 
shall pay as much again as A, and C as much 
again as' B ; what then must each pay? 
Now suppose A to pay 10 1. then B must 
pay 20/. and C 40/. the total of which is 70/. 
but it should be 1 40/. Therefore, if 70/. should 
be 140/. what should 10/. be? 
Answer, 20/. for A’s share, which doubled, 
makes 40/. for B’s share, and that again 
doubled, gives 80/. for C’s share, the total ot 
which is 140/. 
Double position, is when there can be no 
partition in the numbers to make a proportion. 
In this case, therefore, you must make a sup- 
position twice, proceeding therein according 
to the tenor of the question. If neither of 
the s ipposed numbers selves the proportion, 
observe the errors, and whether they are 
greater or less than the supposition requires, 
and mark the errors accordingly with the sign 
-(-or — . See Character. 
Then multiply contrariwise the one position 
by the other error ; and if the errors are both 
too great, or both too little, subtract the one 
product from the other, and divide the dif- 
ference of the products by the difference of 
the errors. If the errors are unlike, as the one 
and the other — , add the products, and 
divide the sum thereof by the sum of the 
errors added together; for the proportion of 
the errors is the same with the proportion of 
the excesses or defects of the numbers sup- 
posed to be the numbers sought ; or the sip- 
positions and their errors being placed as be- 
fore, work by this proportion as a general 
rule, viz. as the difference of the errors if 
alike, or their sum if alike, to the difference 
of the suppositions, so either error, to a fourth 
number; which accordingly added to or sih- 
tracted from the supposition against it, will 
answer the question. 
Position, in geometry, is a term some- 
times used in contradistinction to magnitude : 
thus, a line is said to be given in position, 
positione data, when its situation, bearing, or 
direction, with regard to some other line, is 
given ; on the contrary, a line is given in 
magnitude when its length is given, but not 
its situation. 
POSSE comitatus. See Power or - 
the County. 
POSSESSION is two-fold, actual and in 
law. Actual possession is when a man ac- 
tually enters into lands and tenements to him 
descended. Possession in law, is when the 
lands or tenements are descended to a mart, 
and he lias not as yet actually entered into 
them. Staundf. 198. 
POST, a military station. Thus the de- 
tachments established in front of the army are 
termed out-posts ; the stations on the wings of 
the army are said to be the posts of honour, 
as being the most conspicuous and most ex- 
posed. But in the operations of a campaign, 
a post properly signifies any spot of ground 
capable of lodging soldiers ; or any situation, 
whether fortified or not, where a body of 
men may make a stand and engage the enemy 
to advantage. The great advantages of good 
posts,- in carrying on war, as well as the mode 
of securing them, are only learned by expe- 
rience. Barbarous nations disdain the choice 
of posts, or at least are contented with such 
as immediately fall in their way ; they trust 
solely or chiefly to strength and courage r 
and lienee the fate of a kingdom may be de- 
cided by the event of a battle. But enlight- 
ened and experienced officers make the 
choice of posts a principal object of attention. 
The use of them is chiefly felt in a defensive 
war against «n invading enemy; as, by carry- 
ing on a war of posts in a country where this 
can be done to advantage, the most form- 
idable army maybe so harassed and reduced, 
that all its enterprises may be rendered abor- 
tive. 
In the choice of a post, the general rules 
to be attended to are, that it should be con- 
venient for sending out parties to reconnoitre, 
surprise, or intercept the enemy ; that if pos- 
sible’ it may have some natural defence, as a 
wood, a river, or a morass, in front or tlank, 
or at least that it be difficult of access, and 
susceptible of speedy fortification p, that it 
shall be so situated as to preserve a commu- 
nication with the main army, and have co- 
vered places in the rear to favour a retreat ; 
that it may command a view of all the ap- 
proaches to it, so that the enemy cannot ad- 
vance unperceived and rest concealed, 
while the detachment stationed in the pos- 
are forced to remain under arms ; that it is 
not commanded by any neighbouring heights ; 
and proportioned in extent to the number of 
men who are to occupy and defend it. It is 
not to be expected that all these advantages 
will often be found united; but those posts 
ought to be selected which offer .the ...greatest 
number of them,. 
