722 
P O 
of the orderhemiptera. Generic characters—Bodyovate, 
inflated, diaphanous; head inflefled, armed with jaws; 
thorax convex, carinate beneath ; wing-cafes deflefted, 
membranaceous; legs formed for running. There are 
three fpecies of this genus, natives of the Cape ; and they 
all appear to confift of a mere hollow inflated membrane; 
by rubbing together their ferrate or toothed legs, they 
make a ftirill kind of noife morning and evening; and 
they follow a light; they are fo nearly allied to the cricket 
tribe, that they have been ranked by Fabricius with the 
genus Gryllus. 
1. Pneumora immaculata: green, fpotted with white; 
wing-cafes immaculate. It inhabits the Cape of Good 
Hope. In Fabricius it is the Gryllus papillofus. 
2. Pneumora maculata : wing-cafes green, with fquare 
white fpots. 
3. Pneumora guttata: wing-cafes green, with two 
white fpots ; abdomen with three white lpots on each fide. 
PNIGA'LIUM, f. The incubus, the nightmare. Phil¬ 
lips .—See the article Pathology, vol. xix. p. 189,90. 
PNI'GITIS, f. in the materia medica of the ancients, 
a name given at different periods of time to two different 
fpecies of earth ; the terra pnie/itis of Diofcorides and 
Pliny being a grey marie, and the puigitis of Galen a black 
clay. The 1 alt of thefe is faid to be a very valuable 
aftringent, and is found in many parts of this kingdom, 
particularly in the neighbourhood of London, and well 
deferving to be introduced in the practice of phyfic. 
PNIG'MUS, or Pnix, f. [from nnya, I fuffocate.] A 
kind of fuftbcation, from whatever caufe. It is very often 
ufed to exprefs that of hyfteric fits in women. 
PO, f. [from pot ~\ A liquid meafure in Guernfey, con¬ 
taining half a gallon. 
PO (fee Padus), one of the great rivers of Europe, 
which traverfes the north of Italy from w'eft to eaft. It 
rifes in Monte Vifo, one of the Cottian Alps, flows north- 
eaft to Turin, pafles that capital, and holds an eaftern 
courfe throughout the whole length of Lombardy, fepa- 
rating Aultrian Italy from Parma, Modena, and the 
States of the Church ; and difcharges itfelf by a number 
of mouths into the Adriatic, about thirty miles fouth of 
Venice. In its courfe, which, with windings, is upwards 
of 500 miles, it receives a great number of rivers, flowing 
in full currents from the Alps on the north, and in lefs 
copious but equally rapid ftreams, from the Appenines 
on the fouth. Of thefe tributary waters, the principal 
are the Dora Riparia, the Dora Baltea, the Stura, the 
Oreo, the Selia, the Tanaro, the Ticino, the Adda, the 
Olona, the Oglio, the Mincio, the Croftolo, and the Panaro. 
Riling in a very mountainous country, the Po foon 
becomes a large river, and is fufficiently deep to bear 
boats and barges at thirty miles from its fource ; but its 
current is fo often rapid, that its navigation is at all fea- 
fons difficult, and not unfrequently hazardous. Though 
it pafles in its progrefs upwards of fifty towns, compara¬ 
tively little advantage is derived from it for the convey¬ 
ance of merchandife. Its volume of water is fubjeft to 
fudden increafe from the melting of the fnows, and from 
heavy falls of rain, the rivers that flow into it being 
almoft all mountain-flreams. This w'ould have very de¬ 
finitive eftets in the flat country in the lower part of its 
courfe, were not great dikes conftrufited on either fide, 
to confine it w’ithin its channel. The gravel rolled down 
from the mountains has progreffively raifed the bed of 
the river, and the protecting mounds have been in like 
manner elevated; io that the Po, in the lower part of its 
courfe, prefents the fingular fpeCtacle of a vaft body of 
water, whofe level is higher than that of the adjacent 
country. Its borders, interfperfed with trees and villages, 
difplay great luxuriance of vegetation, and are extremely 
plealant, though by no means piturefque. It gave name 
for a time, to a department of the French empire; alfo to 
two departments of the temporary kingdom of Italy, viz. 
the Upper and Lower Po. This river, like the Rhine, is 
eroded by flying bridges. A poll is fixed in the middle 
P O A 
of the ftream, and a rope conveyed from it to the paftfage- 
raft, by means of a number of fmall boats which form the 
connecting links. Thefe boats, being prefled on by the 
current, guide the raft to the oppofite fide, with no other 
afliftance than that of an oar. The raft confifts of two 
barges boarded over, and railed round. 
PO (Peter del), an engraver of the Italian fchool, was 
born at Palermo A. D. 610, and died at Naples in 1692. 
He travelled to Rome, and was much employed there in 
the adornment of churches both as painter and architeCI, 
and alfo by the SpaniPn ambaflador. Del Po engraved a 
confiderable number of plates, which confift of etching 
mingled with the work of the graver. The general ftyle 
of his art appears to be ftudied from that of Dominichino; 
and the moft diftinguifhed of his prints are St.John Bap- 
tift in the Wildernefs, the Woman of Canaan, and a dead 
Chrift on the Lap of the Holy Virgin, after Annibal 
Caracci; a fet of the cardinal virtues, Prudence, Juftice, 
Temperance, and Fortitude, after Dominichino; the 
Annunciation, the Nativity, and the Flight into Egypt, 
after Pouflin; and Neptune in his Chariot, after Julio 
Romano; all of folio dimenfions. 
Giacomo del Po, and his After Therefa, the fon and 
daughter of Pietro, alfo etched feveral plates, in a ftyle 
refembling that of their father; among which is Sufanna 
furprifed by the Elders, after Caracci, a folio plate, en¬ 
graved by Therefa. 
PO-GAN', a town of China, of the third rank, in 
Koei-tchoo. 
PO-LO', a town of China, of the third rank, in Quang- 
tong, on Tong-river: ten miles w'eft-north-weft of Hoei- 
tcheou. 
PO-YANG', a lake of China, in Kiang-fi, upwards of 
200 miles in circumference, abounding in fifli. The city 
Nan-hang is fituated on the banks of this lake, which is 
the largelt colletion of waters within the Chinefe domi¬ 
nions. For the diftance of fome miles, indeed, on every 
fide of it, the face of the country is one wild and morally 
wafte, covered with reeds and ruffles, and entirely inun¬ 
dated for a part of the year. Not a village is to be feen; 
nor any traces of habitation vifible, except now and then 
a mean and folitary hut for the refidence of a fiflierrnan, 
fo fituated fometimes as to be approached only by a boat. 
Thefe wretched beings fubfift by fiftiing, and by railing 
vegetables on hurdles of bamboo refting upon marlhes, or 
floating upon the furface of the water. Lake Po-yang 
and the adjacent country may literally be termed the com¬ 
mon fewer of China. Rivers flow into it from moft: 
points of the compafs. Several canals have been formed 
from it, and inclofed within high banks for the fecurity 
of veflfels in the feafon of tempefts and inundations. The 
billows of the lake, indeed, rife fometimes to fuch a 
height as to render it, in the opinion of the Chinefe ma¬ 
riners, as dangerous as the fea. In the lake are fcattered 
fmall fandy iflands juft peeping above the furface of the 
water, and covered with humble dwellings, the abodes 
of fiftiermen. The Po-yang, after having collected the 
waters of feveral rivers, empties itfelf into the Yang-tfe- 
kiang, and contributes in no fmall degree to the magni¬ 
tude of that ftream. 
PO-YE', a town of China, of the third rank, in Pe-tche- 
li: twenty-five miles fouth of Poa-ting. 
PO'A, J'. [the Greek word iroa,, a general name for 
grafs, or herbage, is appropriated by Linnteus to this, 
one of the moft common and copious genera of the grafs- 
family.] Meadow-grass ; in botany, a genus of the clafs 
triandria, order digynia, natural order of gramina, or 
grafles. Generic chara&ers—Calyx : glume many-flow¬ 
ered, two-valved, awnlefs, colledfing the flowers into a 
diftich ovate-oblong fpikelet; valves ovate, acuminate. 
Corolla twc-valved ; valves ovate, fliarpilh, concave, com- 
prefled, a little longer than the calyx, with a fcariofe 
margin. Netary two-leaved ; leaflets acute or jagged, 
gibbous at the bafe. Stamina: filaments three,capillary ; 
antherse forked. Piftillum : germ roundilh; ftyles two, 
reflex, 
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