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The Spaniih runt is the longeft bodied of all the pigeons ; it is fhort tegged, and loofe feathered, and does not walk fo upright as the Leghorn runt. Thefe are of a great variety of colours, but are apt to have accidents in fitting, from their fitting too heavy, and often breaking their eggs. The Friefland runt is a large pigeon, and has all its feathers reverted, or looking as if placed the wrong way. The Roman runt is a pigeon of the fame general make with the common kind, but fo large and heavy that it can hard- ly fly.
The Smyrna runt is middle fized, and is feather footed, and that to fuch a degree fometimes, as to look as if there were wings upon the feet ; the feathers of thefe are fometimes four or five inches long, and often pull the eggs and young out of the nefts. The common runt is the common blue pigeon kept for the table, and known to every body. Moore's Columb. p. 42.
Runt is alfo a name given to Canary birds when three years old. See Canary and Passeres Canarienfes.
RUPELLENSIS/*/, in chemiftry, a name given to a pecu- liar kind of fait, invented by Mr. Seignette at Paris, and extolled as a very valuable medicine.
The preparation of it was kept a great fecret, till difco- vered by fome members of the Paris academy. It was found to be a fpecies of fal polycrejlum, and was properly a foluble tartar compofed of cream of tartar, and the fixed fait of common pot-afhes well depurated. This fait is of a very lingular nature ; for though it be a true alcaline fait, it yet is capable of cryftalization, and it does not eafily diflblve in the open air as other fixed falts do ; but, on the contrary, it calcines therein like vitriol and the Glauber's falts. Phil. Tranf. N° 436.
Another peculiar property of it is, that if it be fatiated with vitriolic acids, and the liquor be evaporated, there is ob- tained a fait which has the figure of Glauber's fait, and all the properties requifite to make Mr. Scignette's fait. In or- der to which, take fait of kali or pot-nihes of Alicant well purified one pound ; diflblve it in water, and add to it cream of tartar half a pound : this is about the quantity ufually neceflary ; but the true proportion, in this cafe, can no more be determined than in the making the common foluble tartar, otherwife than by trial every time ; either from the fait of kali's having retained more or lefs humi- dity, or from the tartar's having more or lefs foulnefs. Boil the whole together in order to diflblve the tartar ; and if the quantity of tartar have been too great after the fermentation is over, filtre the liquor, and as it cools the fuperfluous tar- tar will fall to the bottom : after the feparation of the tartar, evaporate the lixivium over a gentle fire to a proper ftandard, and then fet it in a cool place, and there will fhoot fine cryftals. If the liquor be a little too far evaporated, there will be no cryftals formed, but the whole liquor will con- geal into a hard fubftance tranfparent like ice ; but upon diflblving this in more water, it will flioot as fair as it would have done if properly evaporated at firft. The virtues of this fait confift in its being an excellent purge, its dofe is from one to two ounces ; and it is to be diflblved in a large quantity of water.
RUPERT's drops, a fort of glafs drops with long and flender tails, which burft to pieces, on the breaking off thofe tails in any parts, laid to have been invented by Prince Rupert, and therefore called after his name.
This furprifing phenomenon isfuppofed to arife from hence; that while the glafs is in fufion, or in a melted ftate, the particles of it are in a ftate of repulfion ; but being dropped into cold water, it fo condenfes the particles in the external parts of their fuperficies, that they are thereby reduced within the power of each other's attraction, and by that means they form a fort of hard cafe, which keeps confined the before- mentioned particles in their repulfive ftate ; but when this outer cafe is broke by the breaking off the tail of the drop, the faid confined particles have then liberty to exert their force, which they do by burfting the body of the drop, and reducing it to a very peculiar form of powder. This theory feems to be corroborated by making the drops red hot, and letting them cool again by gentle degrees in the open air, for then there is no fuch effect. Yet it muft be allowed, that there is another experiment which feems to impugn this hypothefis ; and that is by grinding away any part of the drop upon a grindftone, when the remaining part continues entire ; though there appears no reafon why it fhould not break, and burft into duft, if the internal parts be the caufe of it ; fince by this means they muft needs be fet at liberty, in the moft ample manner poflible, unlefs it be that in grinding, the vacuities between the internal particles are tilled up with the matter worn off from the ftone 5 and by this means fixing the parts of the glafs next the ftone, they deftroy their repulfive force ; conftitutmg as it were another fort of hard external cafe, which confines the internal particles no lefs than the other did. The hiftory of thefe drops is this ; they were firft brought into England by prince Rupert out of Germany, and fhewn to king Charles II. who communicated them to the Royal Society at Grefham College j and a committe appointed 3
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on this occafion by the Society, gave the following ac . count of them. They muft be made of green glafs well refined, for till the metal, as the glafs men call it, is perfect- ly refined they never fucceed if made of it ; but always crack and break foon after they are dropped into the water. The beft way of making them is to take up fome of the metal out of the pot upon the end of an iron rod, and immediately let it drop into cold water, and there lie till it is cold. If the metal be too hot when it is dropped into the water, the bufmefs does not fucceed, but the drop frofts and cracks all over, and falls to pieces in the water, and every one that does not crack in the water, but lies in it whole till it is quite cool, is fure to be good: there is great nicety in the hitting a due degree of heat in the me- tal, and the workmen who beft know their bufmefs cannot promifc beforehand which fhall fucceed, but often two fail for one that hits right. Some of them froft over the fur- face without falling to pieces, and others break into pieces before the red heat is quite oyer, and that with a fmall noife ; others break foon after the red heat is over and make a great noife, and fome neither break nor crack till they feem to be quite cold ; and others hold together while they are in the water, but fly to pieces with a fmart noife when they are taken out of it; fome do this on the inftant, others an hour or two after, and others will keep feveral days, nay weeks, and at laft fall to pieces without being touched. Neri's art of glafs by Merrett. p. 356. If one of them be taken out of the water while it is hot, the fmall part of the neck and fo much of the thread or ftring it hangs by, as has been in the water, will upon breaking fall into fmall parts, but not the body, though it have as large cavities in it, as thofe which burft in pieces. If one of thefe drops be cooled in the open air hanging on a thread, or on the ground, it becomes like common glafs in hardnefs, folidity, and all other its qualities, and has nothing of the nature of the drops cooled in water. When a glafs drop falls into the water, it makes a hiffing noife, the body of it continues red a pretty while, and there proceed from it many eruptions like fparkles that crack, and make it leap up and move, and feveral bubbles arife from it .till it cools ; but if the water be ten or twelve inches deep thefe bubbles diminifh fo in the afcending, that they vanifh before they attain the fuperficies of the water, where nothing is to be obferved but a little thin fteam. The outfide of the glafs drop is clofe and fmooth like other glafs, but within it is full of fpungy cavities and blebs. The figure is a fort of oval or pear like fliape, fuch as pearls are painted in, the bottom of which is rounded, and the top terminates in a long neck which is ufually varioufly bent and crooked. Almoft all thofe that are made in water have a little protuberance or knob, a little above the largeft part of the body, and moft commonly placed on the fide toward which the neck ends, but fometimes it is upon that fide that lies uppermoft in the vefl'el where it is made. If the water be hot into which the glafs drop is thrown, it always cracks and breaks in the water, either before the red heat is over or very foon after. If dropped into oil they do not mifcarry fo often as when dropped into water : they produce alfo a greater number of large bubbles, and continue longer bubbling than when dropped into water : thofe made in oil have alfo fewer blebs, and fmaller than thofe which are made in water; and frequently they are fmooth all over, not having thofe knobs which the others have. Some part of the neck of thefe alfo, and part of the fmall thread that is quenched in it, cooled, breaks like common glafs ; but if the neck be broken off near the body, and the body held all the while clofe in ones hand, it will crack and break all over ; but even then it flies not into fo fmall parts, nor with fo fmart a force and noife as thofe do which are made in water, and the pieces will hold together till they are parted, and there then appear long ftreaks or rays upon them, pointing toward the cen- ter of the body, and thwarting the little blebs in it. If the drops are dropped into vinegar, they froft and crack, fo that they are fure to fall to pieces before they are cold, and the noife of their falling in is more loud and hiffing than in water, but the bubbles are not fo remarkable. In milk they make no noife nor any bubbles that can be perceived, and never mifs to froft and crack all oyer, and fall to pieces before they are cold. In fpirit of wine they bubble more than in any other of the liquors, and while they remain entire, they tumble to and fro, and are more agi- tated than in other liquors, and they never fail to crack and fall to pieces ; and by that time five or fix of them have been dropped into this fpirit it will be fet on a flame, but it receives no particular tafte from them. In water wherein nitre or fal armoniac have been diflblved they fucceed no better than in vinegar. In oil of turpen- tine, the firft broke as in the fpirit of wine, and the fecond fet it on fire, fo that it could not be ufed again. In quick- filver, being forced to fink by a ftick, it grew flat and rough on the upperfide ; but the experiment could not be perfefled, becaufe it could not be kept under till it cooled. In an ex- periment made in a cylindric glafs like a beaker, filled with
