PIT 
Wlien the smoke, which is here very tliick, 
gives it its blackness ; this is called tar, 
which, on being boiled, to consume more 
of its moisture, becomes pitch. There is 
another method of drawing pitch, used in 
the Levant: a pit is dug in the ground, 
two ells in diameter at the top, but con- 
tracting as it grows deeper; this is filled 
with branches of pine, cloven into shivers ; 
the wood at the top of the pit is then set on 
lire, and burning downvi'ards, the tar runs 
from it, out of a hole made in the bottom ; 
and this is boiled, as above, to give it the 
consistence of pitch. Sec Turpentine. 
Pitch, in music, the acuteness or gra- 
vity of any particular sound, or of the tun- 
ing of any instrument. A sound less acute 
than some other sound with which it is com- 
pared, is said to be of a lower pitch than 
that other sound ; and vice versa. 
PITCHING, in naval affairs, is the ver- 
tical vibration wkich the length of a ship 
makes about her centre of gravity, or the 
motion by which she plunges her head and 
after part alternately into the hollow of the 
sea. This motion may proceed from the 
waves that agitate the vessel, or the wind 
acting upon the sails, which makes her 
stoop at every blast. 
PITCH pipe, in music, an instrument 
used by vocal practitioners to ascertain the 
pitch of the key in which they are about to 
sing. It is blown at one end, like a com- 
mon flute, and being shortened or length- 
ened by a scale, is capable of producing, 
with great exactness, all the semitones 
within its compass. 
Pitch stone, in mineralogy, is of various 
colours, as grey, green, yellow, and red, in 
tiieir several shades, hut generally of the 
paler cast. It occurs in mass. Internally 
it is shining, with a greasy lustre. Its frac- 
ture is conchoidal, passing into splintery, it 
approaches to hornstone. Its fragments 
are angular and sharp-edged. Sometimes 
it occurs in smooth granular distinct con- 
cretions. It is hard, brittle, and easily 
frangible, and the specific gravity is 2.3. 
It is fusible, by means of the blow pipe, 
into a porous enamel. It is composed of 
Silica 64.58 
Alumina 15.41 
Oxide of Iron 5 
84.99 
(Loss 15.01 
100 
PL A 
This mineral occurs in mountain masses, 
and constitutes entire mountains. It forms 
the base of a particular kind of poi phyry, 
and abounds in many parts of Germany and 
Siberia. 
PITTOSPOEUM, in botany, a genus of 
the Pentandria Monogynia class and order. 
Essential character : calyx deciduous ; pe- 
tals five, converging into a lube ; capsule 
two to five valved, two to five celled ; seeds 
covered with a pulp. There are three 
species. 
PIVOT, a foot or shoe of iron, or other 
metal, usually conical, or terminating in a 
poiut, whereby a body, intended to turn 
round, bears on another fixed at rest, and 
performs its circumvolutions. The pivot 
usually bears or turns' round in a sole, or 
piece of iron or brass, hollowed to receive 
it. 
PLACARD, or Placart, among fo- 
reignei s, signifies a leaf of sheet of paper, 
stretched out, and applied on a wall or post, 
containing edicts, regidations, &c. 
PLACE, in law, where a fact was com- 
mitted, is to be alledged insppeals of death, 
indictments, &c. 
Place, in philosophy, a mode of space, 
or that part of immoveable space which 
any body possesses. Place is to space or 
expansion, says Mr. Locke, as time is to 
duration. Our idea of place is nothing but 
the relative position of any thing with re- 
ference to it? distance from some fixed and 
certain points. Whence we say, that a 
thing has «■ has not changed place, when its 
distance either is or is not altered with 
respect to those bodies witli which we have 
occasion to compare it. That lids is so, 
continues that great philosopher, we may 
easily gather from hence, that we have no 
idea of the place of the universe, though we 
can of ail its parts. To say that the world is 
somewhere, means no more than tliat it does 
exist : however, the word place is some- 
times taken to signify that space which any 
body takes up ; and in this sense, according 
to the same autlior, the universe may be 
conceived in a place ; but he thinks that 
this portion of infinite space possessed by 
the material world, might more properly 
called extension. 
Place, in war, a general name for all 
kinds of fortresses where a party may de- 
fend themselves : thus, 1. A strong or forti- 
fied place, is one flanked, and covered with 
bastions. 2. A regular place, one whose 
angles, sides, bastions, and other parts, are 
equal ; and this is usually denominated 
Cc 
VOL. V. 
