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The nineteenth clafs is of the trees and fhrubs which have Catkins or lull for their flowers. Thefe the author fays con- fift either of Jlamina and apices alone, that is, of the threads or capfules of the farina ; or they are compofed of thefe with fome little leaves affixed to a long flcnder axis : Thefe Catkins he obfcrves are always in a different place from the fruit ; and that, fometimes on the fame, fometimes on different trees. Of this clafs are the Walnut, Oak, Beech, &c. The twentieth clafs is of trees and fhrubs, which have a mono- petalous flower ; and of this are the Elm, Lilac, Storax, Olive, Sec.
The twenty iirft clafs is of the trees and fhrubs which have a rofaceous flower ; and among thefe are comprehended the Lime, Sumach, Ivy, Vine, &c.
And the twenty fecond, or laft clafs, is of the trees and ' fhrubs with , a papilionaceous flower ; among which are reck- oned the Broom, Bean, Trefoil, Judas-tree, &c. It is very eafily feen, that this is far from a ftrictly accurate method ; the author has indeed aflifted it with figures, which are very ufeful and inftru&ive ; and, as the judicious Linnseus obferves, more is in reality -to be learned from them, than from all the author has faid. Linnaus has well obferved, that this method is neither perfecl: nor fufficiently diftinctive ; the glory of inftructing the botanift with truth and certainty was indeed rcferved for that author alone, who when he had lhcwn the imperfection and uncertainty of all the before eftaHiihed methods, plan'd out an abfolutely new one, founded on the unalterable parts of plants, their organs of fructification. See the article Fructification, Append.
PETER'S wort, or St. Peter's-ziw/, the Englifh name of a genus of plants, called by botanifts Hypericoides and Afcyrum. See the article Ascyrum, Append.
PETOLA, in zoology, the name of a fpecies of coluber, the fcuta of whofe abdomen are two hundred and nine, and the fquamse of the tail ninety. See the article Coluber, Suppl.
PETREL, the name of a very remarkable bird, called Procel- laria, by authors. See the article Storm-/h^ Suppl. The feet are large, the toes are flcnder, and connected by a fine, thin, black membrane j there is no hinder toe, but the claw in that part is fmall, and connected immediately to the back of the foot. The middle toe is fhorteft, and has only two joints; the outer is longer, and has four ; and the inte- rior has three, and is longer than either. Hill, Hift. Anim.
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PETRIDIA, in Natural Hiftory, the name of a genus of foffils of the Scrupi-kind, of a plain uniform ftruclure, of no great variety of colours, and emulating the external form of peb- bles, oce the article Scrupi, Append. Of this genus the following are all the known fpecies: i. The various fized, pellucid, colourlefs, cryftalline Petri- dm,,:, commonly called Pebble -cryjlal. 2- The purple, femi- peilucio, cryftalline Petridium. 3. The fnow-whitc, opake, crystalline Petridium. 4. The opake, whit ifh, redd ifh, or yellow ifh, cryftalline Petridium, commonly called red, white, or yellow fparry pebbles. 5. The yellowifh-white pumicofe, or fpungy Petridium. 6. The hard, porous, whit'fh, cryf- fcalline, Petridium. 7. The grey ifh- white, opake, ftony Pe- tridium. 8. The friable, fhining, white, arenaceous Petri- dium. 9. The white, cryftalline Petridium, fpotted wi:h fmall yellow dots. 10. The whit ifh- brown, dull Petridium. 11. The blu ifh- white, hard, cryftalline Petridium. 12. The browniih white, hard, fhining Petridium. Vid. Hill, Hift. Kofs. p. 563 — 572.
PUTTY -IVhin, a name by which fome call the Utex, or Ge- nijla Spartium. See the article Genista Spartium, Suppl.
PHACA, in the Linnasan fyftem of botany, the name of a di- ftin£f. genus of plants, called by Tournefort Ajiragaloides . See the article Astragaloides, Suppl.
PHAL/EN7E, in the hiftory of infects, the name by which zoo- Iogifts call the night-butterflies, or moths, as they are vul- garly called. See the article Phalen^e, Suppl.
PHASIANUS, the Pheafant, in ornithology, the name of a genus of birds of the gallinaceous kind. See the articles Gal- ling, and Pheasant, Suppl.
The diftinguifhing characteriftic of this genus of birds, is, that the area or fpace about the eyes is naked, and that they have no wattles.
The fpecies are thefe: 1. The common Pheafant, with a blackifh purple-colout'd breaft. 2. The red, or fcarlet- breafted Pheafant : This is nearly of the fizc of the common Pheafant, and its breaft is of a high fcarlet, and the belly red, but not fo bright. 3. The Eaft-India Pheafant .- This is an extremely beautiful bird, the whole body of which is varie- gated with a profufion of the brighter! colours, yellow, red, blui*fh-green, and almoft every other tinge. Hill, Hilt. Anim. p. 486.
Pheasant's-^, in botany, a name fometimes given to the Adonis. See the article Adonis-^w, Suppl.
Phe as ax r's-eyc Pink, the name of a fpecies of Caryophyllus. See the article Pink, Suppl.
PHOCA (Suppl) — Dr. Parfons has lately given us a differ- tation upon the clafs of the Pboca ?narhi(S, See Phil. Tranf, vol. 47. pag. 109.
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Phoca is the generic name, and all the fpecies have a great likenefs to each other, and may all alike Jiave the names pho- «fl, vitttlus marinus, jea-cow, fea-lion, &c. The manati, the foil or feal, the walrus or mors, are fo many fpecies of this genus. Phil. Tranf. ib. PHYSIC nut, the Englifh name of a diftincT: genus of plants, called by botanifts Rtcinoides. See the article Ricinoides, Suppl. PHRYGANIUM, In the hiftory of infeas, a genus of four- winged flies, of the Neuroptera clafs. See the article Neu- koptera, Append.
The wings of the Phrygania, of which there are a great many fpecies, are incumbent ; they have four tentacula, two on each fide. PICKTOOTH (Suppl.)— Spanijh Picktooth, a name by which fome call the Vifiaga of Ray, a fpecies of Dauais. See the article Daucus, Suppl. PIECES. Plants may be propagated from their cuttings, flips, or Pieces ; and it has been found that fome kinds of animals have the like property, "which may be called a reproduction of the animal or plant from a part of it. See the articles Re- production and Plant, Append, and Polype, Suppl. PIGEON-/V7, a name fometimes ufed for the Cyiifus, or
fhrub- trefoil. See the article Cytisus, Suppl. PILE (Suppl.) — To eftimate the force of the rammer made ufe of to drive Piles, its weight ought to be multiplied into the velocity it acquires in falling. Thus, if a rammer which weighs 500 lb. be let fall from four feet, it will fall that height in half a fecond, and have at the time of percuflion a velocity capable to carry it eight feet in half a fecond, with- out any farther help from gravity ; fo that we muft multiply 500 by j 6, or its weight by the number of feet it would fall in a fecond, and the product 8000 gives the momentum of the ftroke. If a capftan, pullies, or windlas be made to raife the rammer to a confide rable height, and then by an eafy contrivance lopfen it at once from its hook, the momentum of the ftroke will always be as the fquare root of the height from which the rammer fell. Defaguliers, Experim. Phil. P- 336, %
But it is to be obferved, that the effe£t of the blow of the rammer will be as the fquare of its velocity ; that is, as the height from whence it falls, and not as the fquare root of that height. Thus if the blow of the rammer drive the Pile 6 foot deep j a blow given with twice the velocity, will, ceteris paribus, drive it four feet deep. This follows from the nature of the force of bodies in motion. See the article Force, Append.
We have the figure and defcription of a new machine for driving Piles, invented by Mr. Vauloue, in Defaguliers, Ex- perim. Philofoph. p. 417, feq. PiLFj-wort, a name by which fome call the Ranunculus, or
Crowsfoot. See the article Ranunculus, Suppl. PIMPILLO, a name fometimes given to the Opnntia of bota- nical writers. See the article Opuntia, Suppl. PIMPINEL (Suppl.) is alfo a name by which the Sangui- forba, or burnet, of botanifts is fometimes called. See the article Sanguisorba, Suppl. PINASTELLA, in botany, the name by which Dillenius calls ihcHippuris of Linnseus. See the article Hippuris, Suppl. PINASTER, the name of feveral fpecies of pine. See the ar- ticle Pine, Suppl. Ground-PiNE, or Vwarf-FiKE, names by which the Chama- pitys of botanical writers is fometimes called. See the article Cham^pitys, Suppl. ffiild-PiNE, a name fometimes given to the Karaias, or Ana- nas, of botanical writers. See the article Ananas, Suppl, PINQUIN, or Penqjjin, the names by which the Ananas of Tournefort is fometimes called. ■ See the article Ananas, Suppl. PINK (Suppl.) — oYtf-PiNK, a name by which fome call the
Statice. See the article St atice, Suppl. PINTLE (Suppl.) — Prie/l's Pintle, a name fometimes given to the Arum, or wake-robin. See the article Arum, Suppl. PIPE (Cycl.) — Air-PiVE, an invention of the late ingenious Mr. Sutton to clear fhips of foul air. This he does by a Pipe, the branches of which are laid in the hold, and the extremity of which is fixed into the afh-hole of the furnace. Mr. Watfon has fhewn how thefe Pipes may be laid, fo as to be no way inconvenient, and relates the fuccefs of a trial of them, made on a hulk. See Phil. Tranf. N°462. p. 12. We have now three different contrivances publifhed for cleaning fhips, and other clofe places, of foul air. One by Dr. Defaguliers, which will change the air in the chamber of fick people, in a little time ; either by drawing out the foul air, or driving in frefh ; or doing both fucceffive- ly, without opening doors or windows. See Phil. Tranf.
N °437-
The other by Mr. Sutton before mentioned ; and the third by means of Dr. Hale's ventilators, which feems to be the moft expeditious and fimple method. See the article Ven- tilators, Append. VivE-tree, the Englifh name of a genus of plants, called by botanifts Lilac and Syringia. See the articles Lilac and Sv-
RINGIA, Suppl.
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