PUN 
PUR 
PUS 
524 
th s air- vessel the water from the main pipe 
enters through the exit-valve, and compresses 
the air in the vessel ; which again, by its ex- 
pansion or elasticity, acts upon the water 
(the regress of which is prevented by the 
shutting of the exit-valve); and the water 
rises through the ascending pipe, and by re- 
peated strokes acquires the desired height. 
rive dimensions of the air-vessel, as well 
jH its form and position, whether above, or 
laterally affixed to, the main pipe, are in 
great measure arbitrary ; but its contents ot 
air ought nut to be much less than ten times 
the quantity of water to be raised through 
the ascending pipe each stroke ; and if much 
larger still the better, the principal boundary 
being expence. 
The stop-valve may be opened and shut, 
as has been described in the first method, by 
the mechanism shewn in the figure, or by 
any of the mechanism as shall be adapted 
to the opening of valves. 
Another method is shewn by figs. 13, 14, 
and 15, and is applicable in cases where the 
water to be raised is below the level of the 
main pipe, and is to be discharged at that 
level : which cases occur in the drainage of 
marshy lands, where the action of the cur- 
rent of water of an embanked river, or other 
stream or source of water on a higher level, 
can be employed ; or this method can be ap- 
plied in raising water out of the holds of 
ships, or other vessels, by the motion of 
the vessel through the water. 
This is explained by figs. 13, 14, and 15, 
where C is the main-pipe, A is the receiving 
valve, B the stop-valve, opening outwards, 
]) the ascending or sucking pipe, J the air- 
iressel, and E the weight. 
The water in the main pipe having ac- 
quired a proper velocity, the stop-valve 
suits: the water in the main pipe, continu- 
iag its motion for a time, draws air out ot 
tie air-vessel. Then the momentum of the 
water in the main pipe being expended, the 
receiving valve shuts, and the stop-valve 
epens, the water regains its velocity, and the 
operation is repeated ; and thus, in a few 
sirokes, (the exhaustion increasing,) the air- 
•vessel sucks up water from below, by the 
ascending pipe; and this being continued, 
pie latter pipe fills by degrees to the top ; 
after which, at every successive stroke, a por- 
ton of the water from below passes into the 
jaain pipe, and is carried off, with the upper 
yater, to the place of delivery. 
Jii-Vvup. See Pneumatics. 
PUNCHEON, a little block or piece of 
{teel, on one end whereof is some figure, 
litter, or mark, engraved either in creux or 
jelievo, impressions of which are taken on 
jietal, or some other matter, by striking it 
yrth a hammer on the end not engraved. 
f 'here are various kinds of these puncheons 
ised in the mechanical arts ; such for instance 
; re those of goldsmiths, cutlers, pewterers, 
icc. See also Coinin g. 
Puncheon, in carpentry, is a piece of 
limber placed upright between two posts, 
v’nose bearing is too great, serving, together 
vith them, to sustain some large weights. 
Phis term is also use 1 tor a piece of timber 
,aised upright, under the ridge of a building, 
vherein the little forces, ic are jointed. 
Puncheon is also used for the arbor, or 
n ine pal part of a machine, whereon it turns 
^rtically, as that of a crane, &c. 
Puncheon is also a measure for liquids, 
containing a hogshead and one-third, or 
eighty-four gallons. 
PUN1CA, t he pomegrarntt'-tree : a genus 
of the monogynia order, in the icosandria 
class of plants, and in the natural method 
ranking under the 39th order, pomacete. 
The calyx is quinquelid, superior; there are 
live petals ; the fruit is a multilocular and 
polyspermous apple. 
The species are, 1. The granatum, or 
common pomegranate, with a tree stem, 
branching numerously all the way from the 
bottom, growing eighteen or twenty feet 
high ; with spear-shaped, narrow, opposite 
leaves ; and the branches terminated by 
most beautiful large red flowers, succeeded 
by large roundish fruit as big as an orange, 
having a hard rind filled with soft pulp and 
numerous seeds. There is a variety with 
double flowers, remarkably beautiful ; and 
one with striped flowers. 2. The nana, or 
dwarf American pomegranate, with a shrubby 
stem, branching four or five feet high, with 
narrow short leaves, and small red flowers 
succeeded by small fruit ; begins flowering 
m June, and continues till October. Both 
these species are propagated by layers : the 
young branches are to be chosen tor this pur- 
pose, and autumn is the proper time for lay- 
ing them. 
The dried flowers of the double-flowered 
pomegranate are possessed of an astringent 
quality ,* for which reason they are recom- 
mended in diarrhoeas, dysenteries, &c. where 
astringent medicines are proper. The rind 
of the fruit is also a strong astringent, and 
as such is occasionally made use of. 
Pupil. See Anatomy, Optics, and Phy- 
siology. 
PURCHASE, in law, the buying or ac- 
quiring of lands. See. with money, by deed 
or agreement, and not by descent or right of 
inheritance. A joint purchase is when two 
or more persons join together in the pur- 
chase. Purchasers of lands are to take no- 
tice of all charges thereon : there are, how- 
ever, certain statutes to guard against frau- 
dulent incumbrances. The court of chan- 
cery will relieve the purchaser of a term 
against a title that lay dormant, where money 
has been laid out on improvements. 
Purchase, in the sea-language, is the 
same as draw in : thus when they say the 
capstan purchases apace, they only mean it 
draws in the cable apace. 
PURITAN, a name formerly given in de- 
rision to the dissenters from the church of 
England, on account of their professing to 
follow the pure word of God, in opposition 
to all traditions and human constitutions. 
PURLINS, in building, those pieces of 
timber that lie across the rafters on the in- 
side, to keep them from sinking in the middle 
of their length. 
PURPLE, a colour composed of a mix- 
ture of red and blue. 
A beautiful transparent purple for painting 
may be made by boiling four ounces of 
rasped Brasil-wood in a pint of stale beer, 
and half an ounce of logwood, till the liquor 
1 is heightened to the colour you desire, which 
may be known by dipping a piece of paper 
in it. If you find it tooTed, add a quarter 
of an ounce more of logwood, which will 
render it still deeper; and by this method 
you may bring it to any degree of purple, 
bv putting either more or less logwood to 
tlie former composition, and fixing it with 
alum. This will produce such a clear purple^ 
as no mixture of reds and blues will pro- 
duce. Madam Mariana of Amsterdam, fa- 
mous for painting in miniature, and for her 
excellent manner of illuminating prints, says, 
that the best purple that can be made, may 
he composed between the carmine and in- 
digo ; to strengthen which on the red side, 
you may add lake, between the lighter and 
darker part: and lake, when it is used in 
the same way on the foregoing purple, pro- 
duces a very fine effect. See D v eing. 
PURPURA. SeeMuRCA. 
PURSER, an officer aboard a man of war, 
who receives her victuals from the victualler, 
sees that it is well stowed, and keeps an ac- 
count of what he eveiy day delivers to the 
steward. He also keeps a list of the ship’s 
company, and sets down exactly the day of 
each man’s admission, in order to regulate 
the quantity of provisions to be delivered out; 
and that the paymaster or treasurer of the 
navy may issue out the disbursements, and 
pay off the men, according to his book. 
PUS. The liquid called pus is secreted 
from the surface of an inflamed part, and 
usually moderates and tennifiates the in- 
flammation. It assumes different appear- 
ances according to the state of the sore. 
When it indicates a healing sore, it is called 
healthy or good-conditioned pus. This li- 
quid possesses the following properties: 
It is of a yellowish-white colour, and of 
the consistence of cream. Its taste is insipid, 
and it has no taste when cold. Before the 
microscope it exhibits the appearance of 
white globules swimming in a transparent 
fluid. 
It produces no change on vegetable blues. 
When exposed to a moderate heat it gra- 
dually dries, and assumes the appearance of 
horn. When exposed to destructive distil- 
lation, Bergman obtained first abort one- 
fourth of the pus in the state of insipid wa- 
ter. On increasing the fire, a liquid came 
over containing abundance of ammonia, and 
accompanied by gaseous bodies, which were 
not examined. Some concrete carbonat of 
ammonia sublimed, accompanied by empy- 
reumatic oil. A light brilliant coal remained 
of difficult incineration. The ashes gave 
traces of iron. 
When pus is left exposed to the air, it 
gradually becomes acid, according to Ililde- 
brant ; and Haller affirms that it sometimes 
gives a red colour to litmus even when re- 
cent. When thrown into water it sinks to 
the bottom. When agitated, the mixture 
becorpes milky ; but the pus separates again 
when allowed to remain undisturbed. By 
repeated agitation, however, and especially 
by the application of heat, a milky liquid is 
obtained, which passes in that state through 
the filtre. 
Alcohol thickens pus, but does not dis- 
solve it ; neither does pus unite with oils. 
Sulphuric acid dissolves it, and forms a 
purple-coloured solution. When diluted with 
w ater, the dark colour disappears, and the 
pus separates ; either sinking to the bottom, 
or rising to the surface, according to the 
quantity of water added, and the time that 
the solution has been allowed to stand. Di- 
J luted sulphuric acid does not act upon it. 
