PRI 
first to set up a page, for instance, in the 
common way, with moveable types ; and 
when it is rendered as correct as the nature 
of the thing will admit, a cast is taken from 
it, and in this cast the metal for the stereo- 
type plate is poured-j and so for every page 
or sheet of a work intended to be stereo- 
typed. When the plates are prepared,^ they 
are printed olF at the Stanhope press ; and 
it must be confessed, that the works hi- 
therto published, that have been printed in 
this manner, are very beautiful, and to the 
full as correct as the best editions of books, 
printed according to the common method. 
But as it does not appear that any actual 
saving can bo obtained in the manufacture 
of books in general, the London publishers 
have not yet thought it worth their while 
to patronize and encourage this curious in- 
vention. 
PRISM, in geometry, an oblong solid, 
contained under more than four planes, 
whose bases are equal, parallel, and alike 
situated. The prism is generated by the 
motion of a rectilinear figure, descending 
always parallel to itself, along a right line. 
If the describent be a triangle, the body is 
said to be a triangular prism ; if square, a 
quadrangular one, &c. 
From the genesis of the prism, it is evi- 
dent it has two equal and opposite bases, 
and it is terminated by as many parallelo- 
grams as the base consists of sides: and 
that all the sections of a prism parallel 
to its base are equal. Every triangular 
prism may be divided into three equal 
pyramids. 
To measure the surface of any prism, 
find the area of each side, whether a trian- 
gle, parallelogram, or other rectilinear 
figure, as directed under these articles, and 
the sum of all these, taken together, is the 
whole superfices of the prism. The solid 
content of a given prism may be found 
thus : let the area of the base of the prism 
be measured, as directed under the article 
Mensuration ; and let this area be mul- 
tiplied by the height of the prism, and the 
product will give the solid content of the 
prism. 
Prism, in dioptrics, a triangular glass- 
prism, much used in experiments about the 
nature of light and colours. See Optics. 
PRISTIS, the sawfish, in natural his- 
tory, a genus of fishes of the order Cartila- 
ginei. It may be with more propriety con- 
sidered as a species of the squalus, or shark, 
and as such is regarded by Shaw. The 
saw-fish inhabits the Mediterranean, and 
PRO 
was known to the Greeks and Romans kf 
the name of pristis. It grows to the length 
of sixteen feet, and the general length of 
the snout is about one third of that of the 
whole fish. There are three varieties, in 
which the difference is confined to the size 
and the snout. 
PRIVATEERS, in maritime affairs, a 
kind of private ships of w'ar, fitted out by 
private persons at their own expense ; who 
have leave granted them to keep what they 
can take from the enemy, allowing the 
Admiral his share. 
PRIVY council, is the principal council 
belonging to the King, and is generally call- 
ed by way of eminence the council. Privy 
Counsellors are made, by the King’s nomi- 
nation, without either patent of grant; and 
on taking the necessary oaths they become 
immediately Privy Counsellors, during the 
life of the King that chooses them, but sub- 
ject to removal at his discretion. No in- 
convenience now arises from the extension 
of the number of the Privy Council, as- 
those only attend who are especially sum- 
moned for that particular occasion. 
PRIZE, in maritime affairs, a vessel taken 
at sea from the' enemies of a state, or from 
pirates ; and that either by a man-of-w'ar, a 
privateer, &c. having a commission for that 
purpose. Vessels are looked on as prize, if 
they fight under any other standard than 
that of the state from w’hich they liave their 
commission ; if they have no charter-party, 
invoice, or bill of lading a board ; if loaded 
with effects belonging to the King’s ene- 
mies, or with contraband goods. Those of 
the King’s subjects recovered , from the 
enemy, after remaining twenty-four hours 
in their hands, are deemed lawful prize. 
Vessels that refuse to strike may be con- 
strained ; and if they make resistance and 
fight, become lawful prize, if taken. If ships 
of war, the prizes are to be divided among 
the officers, seamen, &c. as his Blajesty 
shall appoint by proclamation ; but among 
privateers, the division is according to the 
agreement between the owner. By statute 
13 George II. c. 4. Judges and officers, 
failing of their duty, in respect to the con- 
demnation of prizes, forfeit 500/. with full 
costs of suits ; one moiety to the King, and 
the other to the informer. 
PROBABILITY is nothing but the ap- 
pearance of the agreement or disagreement 
of two ideas, by the intervention of proofs 
whose connections is not constant and im- 
mutable, or is not perceived to be so ; but 
is, or appears for the most part to be so j 
