Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/261

 P L A

P L A

ibver, lofe its -fluidity immediately upon- the tefllit ion thereof Boyle's Works abr. Vol. I. p 313.

Two or three fpoonfuls of' burnt alaba'fter, mixed up thin with water, in a lhort time coagiilate, at the bottom of a vef- Tel full of water, into a hard lump, notwithftandwig the water that furroiinded it. Artificers obferve, that the coagulating property of burnt alabafter will be very much impaired pf *I6ft| ir the powder be kept too long, especially if in the open air, before it is made ufe of; and when it hath been once tempered with water, and fuffered to grow hard, they cannot by any burning or powdering of it again, make it ferviceable for their purpofe as belore. Beyle's Works abr. Vol. J. p. 341.

This matter, when wrought into vefleis, &c. is ftill of Co loofe and fpungy a texture, that the air has eafy paflage thro' it. Mr. Boyle gives an account among his experiments with the air -pump, of his preparing a tube of this pia/fer, clofed at one end and open at the other, and on applying the open end to the cement, as is ufually~done with the receivers, it was found utterly impoffibie to exhauft all the air out of it; for frefli air from without prefled in as fair, as the other, or internal air, was exbauffed, tho' the fides of the tube were of a confiderable thicknefs. A tube of iron was then put on the enj Ve; {o that being filled with water, the tube oi' plajier of Par s was covered with it ; and on ufmg the pump, it was immediately (ecn, that the water pafled through into it as eafily as the air had done, when that was the ambient fluid. After this, trying it with Venice turpentine inftead of water, the thing fucceeded very well; and the tube might be per- fectly exhausted, and would remain in that ftate feveral hours. After this, on pouring feme hot oil upon the turpentine, the cafe was much altered ; for the turpentine melting with this, that became a thinner fluid, and in this ftate capable of paiTing like water into the pores of the plajler. On taking away the tube after this, it was remarkable that the turpentine, which had pervaded and filled its pores, rendered it transpa- rent, in the manner that water gives tranfparency to that An- gular (lone called Qculus mttndi. In this manner, the weight of air, under proper management, will be capable of making ' feveral forts of glues penetrate plajier of Paris ; and not only this, but baked earth, wood, and at! other bodies porous enough to admit water on this occafion. Philof. Tranf. N. 122.

PLASTERING. The modern taftc runs greatly into plajler- ing; and it were much to be wiflied that this art could be again brought to its antient perfection. In our beft buildings -the plajiercd walls and ceilings crack and fly, and in a little time grow damp, or moulder to decay. The Romans had an art of rendering their works of this kind much more firm and durable, and there is no reafon to defpair of reviving this art by proper trials.

The antient plajler'mg of thefe people, prefcrved to this time, where it has not met with violent blows or injuries from ac- cidents, is ftill found as firm and folid, as free from cracks or crevices, and as fmooth and polifhed on the furface, as if made of marble. The bottoms and fides of the Roman aqueducts were made of this flajitring, and endured many ages without hurt, unlefs by accidents ; witnefs that whereof fome yard; are Mill to be found on the top of the Pont de Garde, near Nifmcs, for the fupport of which that famous bridge was built to carry water to the faid town. The roofs of houfes. and the floors of rooms at Venice arc covered with a fort of plajier^ made of later date, and yet flrong enough to endure the fun and weather for feveral ages, without cracking or fpoii- ing, and without much injury from people's feet. The fecret of preparing this Venetian plaficr is not among us ; but it would be worth while to try whether fuch a fub- ftance might not be made by boiling the powder of gypfum dry over the fire, for it will boil in the manner of water; and when this boiling or recalcining was over, the mixing with it refin, or pitch, or both together, with common fulphur, and the powder of fca-fhclls. If thefe were all mixed together, and the water added to it hot, and the matter all kept hot upon the fire till the inftant of its. being ufed, fo that it might be laid on hot, it is pofliblethis fecret might be hit upon. Wax and oil of turpentine may be aJfo tried as additions : thefe being the common ingredients in fuch cements as we have accounts of as the firmed. Strong ale-wort is by fome directed to be ufed, inftead of water, to make mortar of Iime- ffone be of a more than ordinary flrength. It is pofiible, that the ufe of this tenacious liquor to the powdered ingredients of this propofed tla/ic, might greatly add to their folidity and firmnefs. Phil. Tranf. N". 93.

PLAT (Cyd.) — Plat-wjh;, in the manege, called in French avs<, are the veins in which we bleed horfes, one in the lower part of each fhoulder, when we blood a horfe in the fhoul- ders ; and in -the flat part of the thighs.

Pi. ats, in a fhip, flat ropes made of rope-yarn, and weaved one over the other : they ferve to fave the cable from galling in the hawfe, or to wind about the flukes of the anchor- -, to fave the pennant of the fore-fheet from galling againft them.

PLATANUS, the plane tree. See ?l a s**trte.

PLATTE, a word ufed by fome anatomical writers to exprefs the feapujas. 2

PLATAMON, a word ufed to exprefs a low and imooth rockj juft appearing above water.

PLATAN-ARIA, in botany, a name by which fome authors have called the ffar-garmnii or burr-reed, from its round echi- nated fruit, which in fhipe and fize much refembie thofe of the platatius.

PLA I E, (Cy'cl.) a term ufed by our fportfmen to exprefs the reward given to the beft horfe at our races. . he wmning a pfale is not a work of a few days> to the owner of the horfe, hut great care and preparation are to be made for it, if there is any great dep'endancs on the fticcefs. A month is the leaft time that can he allowed to draw the horfe's body clear, and to refine his wind to that degree of perfection that li, attainable by art.

It is firft necefiary to take an exact view of his body, whether he be low or high in flefh ; and it is.alfo neceffary to Confiderj whether lie be dull and heavy, or brlfk and lively when abroad. If he appear dull and heavy, and there is reafon to fuppofe it is owing to too hard riding; or, as thejockies ex- . prefs it, to fome greafe that has been diflblved in bunting, and has not been removed by fcouring, then the proper remedy is half an ounce of diapente, given in a pint of good fack ; this will at once remove the caufe, and revive the creature's fpirits. After this, for the firft week of the month, he is to be fed with oats, breaii, and fplit beans, giving him fometimes the one, and fometimes the other, as he likes beft ; and always leaving fome in the locker, that he may feed at leifure when he is left alone. When the groom returns at the feeding time, whatever is left of this muft be removed, and frefh given j by this means the creature will foon become high fpirited, wanton, and full of play. Every day he muft be rode out art airing, and every other day it will be proper to give him a little more exercife; but not fo much as to make him fweat too much.

The Leans and oats in this cafe are to be put into a bag, and beaten till the hulls are all off, and then winnowed clean ; and the bread, inftead of being chipped in the common way, is to have the cruft clean cut off.

If the horfe be in good flefh and fpirits when taken up for its month's preparation, the diapente muft be omitted; and the chief bufmefs will be to give him nood food, and fo much exercife as will keep him in wind, without over iu rating or tiring his fpirits. When he takes larger exercifes afterwards, towards the end of the month, it will be proper, to have fome horfes in the place to run againft him. This will put him upon his mettle, and the beating them will give him fpirits. This, however, is to be eautioufly obferved, that he has not a bloody heat given him for ten days or a fortnight before the plate is to be run for; and that the laft heat that is given him the day before the race, muft be in his cloaths: this will make him run with greatly more vigour, when ftripped for the race, and feeling the cold wind on every part. In the fecond week the horfe fhould have the fame food and more exercife, and in the laft fortnight he muft have dried oats, that have been hulled by beating ; after this they are to be wetted -in a quantity of whites of eggs, beaten up, and then laid out in the km to dry ; and when as dry as before, the horfe is to have them. This fort of food is very light of di/eftion, anct very good for the creature's wind. The beans in this time fhould be given more fparingly, and the bread fhould be made? of three parts wheat, and one part beans. If he fhould be- come collive under this courfe, he muft then have fome ale and whites of eggs beaten together : this will cool him, and keep his body moift.

In the laft week the mafh is to be omitted, and barley-water given him in its place, and every day, till the day before the race : he fhould have his fill of hay, then he muft have it given him more fparingly, that he may have time to digeft it ; and in the morning of the race-day, he muft have a toaft or two of white bread, foaked in fack, and the fame juft before he is Jed out to the field. This is an excellent method, be- caufe the two extremes of fullnefs and faffing are at this time to be equally avoided ; the one hurting his wind, and the other occafioning faintnefs, that may make him lofe. After he has had his food, the litter is to be {hook up, and the ffable kept quiet, that he may be difturbed by nothing till he is taken out to run.

Plates, in gunnery. The prife-phtes are two plates of iron on the cheeks of a gun-carriage, from the cape-fquare to the center, through which the prife-bolts go, and on which the hand-fpike refts when it poifes up the breech of the piece* Breaft-/>/tfto are the two plates on the face of the carriage, one on each cheek. 'Train-plates are the two plates on the cheeks at the train of the carriage. Dulidge-/>/ofc>' are the fix plates on the wheel of a gun-carriage, where the fellows are joined together, and ferve to ftrengthen the dulidges.

Plate-/c»?c, in the manege, a woven ft rap, four fathom long, three fingers broad, and as thick as one. It is ufed for railing a horfe's legs and fometimes for taking him down, in order to facilitate feveral operations of the farrier. Some impro- perly give the name of platc-lovge to a martingale. See the article Ma itingale, Cyd.

PLATEA, in zoology, the name of a bird of the long-necked kind, approaching to the nature of the itork and heron, and

called