Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/268

 P O G

P O I

With a fiflurt at its extremity, and fhould therefore rather be made of filver than of any other metal. Befide thefe, there fhould be an ordinary fpatula for fpreading plaifters, oint- ments, and cataplafms ; and fometimes by means of their fulcated extremity they are of fervice in railing up fractured bones, of the cranium j feveral needles muftalfo be kept here, fome ftrait and others crooked, for the Pitching up of wounds, taking up of arteries, and many other ufes. Heijler's Surg. p. 1 2.

Pocket medicines. See the article Medicine.

POCO allegro, in the Italian mufic, is not fo fall as allegro.

Poco largo, intimates to play or fing a little flow. See Largo.

Poco-wwwfl allegro, is ufed to fignify that the part it is join- ed to fhould be placed or fung in a little lefs gay manner than allegro requires.

Poco pre/fo, ferves to let us know that we ought to fing or play the part to which it is annexed, not quite lb quick as prejlo requires it fhould.

POCUMMA, in botany, a name given by the people of Guinea, to a fpecies of plant which they ufe as an allringent. Their manner of taking it is very fingular ; for they put the leaves among their dough, and bake them into a mafs with the bread, and then eat the whole together in their food. Phil. Tranf. N° 232.

POD, among botanifls, a fpecies of peritarpium, confuting of two valves which open from the bafe to the point, and are feparated by a membranaceous partition, from which the feeds hangbyakind of funiculus umbilicalis. SeePERicARPiuM.

PODAGRA, a fpecies of the gout. See the article Gout.

Podagra lint, in botany, a name given by fome of the later Greek writers to cufcttta, or dodder, when found grow- ing on the linum or flax. The Latins have called this epili- num, as they do the dodder growing on thyme epithymum ; the earlier Greeks called this linozoftes, Where this dodder takes root in a field of flax, it generally occupies many plants ; and where it twines round them it caufes protuberances and fwellings, and has therefore been refembled to the gout on that plant.

PODAGRARIA, in botany, a name given by many authors to the lefTer wild angelica, called alfo herha Gerardis. Parkin. Theat. p. ^43.

PODER1S, in antiquity, a robe hanging down to the feet ; but it is chiefly ufed to exprefs a linnen garment, a furplice, a ■ fhirt. The Jewifh priefts were covered with this kind of long furphces, during the time of their attendance in the temple; and this was the proper habit of their order. Cal- met, Dift. Eibl.

The word is Greek rnhfyw* from nwj, pes, and «fw, apto. Vid. hlederic. Lex. man. Gra?c. in voc.

PODICEPS, in zoology, a name given by many to the feveral kinds of eolymbi, or divers, as they are alfo called in Englifh arfe foots ; from their legs being placed very backward on their bodies, by which means they have great advantages in fwimming and diving. Ray's Ornithol. p. 256. See the ar- ticle COLYMBUS.

PODISMUS, Uoho-fto^ among the Greeks, a certain fpace, or number of feet laid out by furveyors ; it was the fame with what the Romans called pedatura. Pitifc, in voc. See the article Pedatura.

PODIUM, in the theatre of the antients, the wall that fepa- rated the orchcflra from the fcene. Mem. de l'Acad. Vol. I. p. 190. See Orchestra and Scene, Cycl.

POE A NOPSIA, n«aiw,J/i«, in antiquity, a name fometimes given to the fellival Pyanepfia. See Pyanepsia, Cycl.

POENITENTES, in the church of Rome, a defignation given to heretics, who being admonished by the ecclefiaftical judge, have abjured their errors, and given fufficient fatisfaition to the bifhop or inquifition. Confiscation of goods is a punifh- ment common to all heretics ; but if they confefs and abjure of their own accord, without being formally profecuted, this part of their punifhment is ufually remitted. Hofm. Lex. Univ. in voc. See Inquisition, Cycl.

POGGE, or Cataphractus, in zoology, the name of a fmall fea-fifh, caught in the Englifh and fome other feas. It feldom grows to more than five inches in length ; its head is of a triangular figure, and flatted, and is very broad, and is furrounded at the fides with a number of tubercles.; the forepart toward the mouth has a number of extremely fine hairs, and the hinder part armed with a number of prickles ; the points of which are directed backwards. Its fnout is fhort, and armed with four points ; the two anterior ones re- fembling a horned moon, and the others being prickles with their points turned backwards. The mouth is in the lower part of the head, and is of a femi-circular form, and has two beards at its angles, and a number of hairs under its chin. The body of this 'fifh, near its head, is flatted and of an oc- tangular form ; near the tail it is hexangular, and is of a brownifh colour variegated with black fpots. It is covered all over with bony fcales, in the middle of which there rifes a crooked tumor; which being continued thro' the whole number, makes the body of an angular form : toward th; tail it grows very flender. ft has two fins at the gills, twe more on the belly, and two on the back, all fpotted with black fpots ; and its tail ends in a fmall rounded fin. It ha^

no teeth, but very rough and rigid lips, and lives on flirimps and other fuch food. It is a very well tailed fifh. It is caught not unfrequently on the coafts of Yorklhire, and in great plenty in the mouth of the Elbe. IViLugbbfs Hilt. Pifc. p. 212. See Tab. of Fifh. N". 30. There is an American cataphraclus, much refembling this, but having three angles on the hinder part of its head, one on each fide, and the third in the middle; and its upper chap elliptic, and its mouth a little prominent Its head is cover- ed with a brown and bony helmet; and its back, fides, and tail, with fcales of the fame colour, engraven with fmall pa- rallel lines, and of a rhomboidal figure. Its bellv is covered with a thin limber fkin. Grew's MuTeumj Soc. Reg. p. 117.

POGO, a name by which the inhabitants of the Philippine iflands call their quail : it is very like our common quail, but (mailer.

POINCIANA, in botany, the name of a genus of plants, the characters of which are thefe : The flower is of the roface- ous kind, and is ufually compofed of five petals arranged in a circular form, and filled up in the middle with a larger num- ber of crooked flamina. The cup is divided into five leaves the lower of which is crooked and imbricated ■ from this arifes the piflil, which finally becomes a hard pod of a flatted fhape, which when ripe opens into two parts, and contains a num- ber of roundifh feeds divided from one another by a fort of membranaceous partitions.

There is only one known fpecies of the poinciana, which is the plant called by many crijla pavonis, and purple- flowered acacia- Town. Infl. p. org.

POINSON, in the manege, is a little point or piece of fharp- pointed iron, fixed in a wooden handle, which the cavalier holds in his right hand when he means to prick a leaping horfe in the croupe, or beyond the end of the faddle, in or- der to make him yerkout behind.

POINT, (Cycl.) in geometry, is the termination of a line, and cannot be conceived to have parts. See Surface. Hobbes defines a point to be a body whofe magnitude is not confidered. But his falfe notions of a point, line, and fur- face, have led him into many errors. Monfieur de Crouzas alfo has fuppofed a line to be compofed of points, in his Geo- metry and comment on the analyfc des infiniment petits. This fuppofition only tends to confound learners. See Jo. Bernoulli Oper. Vol. IV. p. 161, feq.

Conjugate Point, in geometry, is ufed for that point Into which the conjugate oval, belonging to fome kinds of curves, va- niflies. Mac Law, Algebr. p. 308.

Point of contrary flexure. The points of contrary flexure and reflexion of curves, are ufually determined by fuppofing the fecond fluxion of the ordinate to be nothing or infinite, that is, >'— 0, oroo, or ddyz=o, or co. See VHopital Analyfe des Inf. petits.

But this rule is liable to feveral exceptions, as is fhewn very fully and clearly by Mr. Mac Laurin in his Treatife of Fluxi- ons, B. i. ch. g. and B. ii. ch. 5. art. 866. The ordinate y panes thro' a point of contrary flexure, when, the curve being continued on both fides of the ordinate, y is a maximum, or minimum. But this does not always happen when >— 0, or co. Mr. Mac Laurin obferves, in general that if y, y, y, &c. vanifh, the number of thefe fluxions be- ing odd, and the fluxion of the next order to them havino- a real and finite value ; then y panes thro' a point of contrary flexure ; but if the number of thefe fluxions that vanifh be even, it cannot be faid to pais thro' fuch a point ; unlefs it mould be allowed that a double infinitely fmall flexure can be formed at one point. Lib. cit. art. 866.

The curve being fuppofed to be continued from the ordinate y, on both fides, ifji be infinite, the extremity of the ordi- nate is not therefore always a print of contrary flexure, as y is not always, in this cafe, a maximum, or minimum; and the curve may have its concavity turned the fame way on both fides of the ordinate. But thefe cafes may be diftin- guilhed by comparing the figns of y on the different fides of the ordinate; for when thefe figns aredifferent, the extremity of y meeting the curve is a point of contrary flexure. Thefuppofitions .)'— 0, orco ,andofy:=o, or cc, ferve to direct us where we are to fearch for the maxima and minima, and for points of contrary flexure ; but we are not always fure of finding them. For tho* an ordinate or fluxion that is pofitive, never becomes negative at once, but by increafing or decreafing gradually, yet after it has decreafed till it vanifh, it may thereafter ra~ creafe, continuing flill pofitive; or after increafing till it be- comes infinite, it may thereafter decreafe without changing its fign. See Mac Laurin, art. 262, 867.

Point of reflexion^ in geometry, is commonly ufed inflead of point of retragradataon, or retrogrefiion. See the article Re-

TROGRADAi'ION, Cycl.

The general rule given by the .Marquis de L'Hopital, for find- ing the point of reflexion in curves whofe ordinates are pa- rallel, is the fame as that for finding the point of contrary flexure, and confifts in taking the fecond fluxion of the or- dinate of ti e curve, and fuppofing it nothing or infinite : but this rule admits of many exceptions. See Mac Laurin's Fluxions, B. i. ch. 9. and B. ii. ch. 5.

Point