Page:Cyclopaedia, Chambers - Supplement, Volume 1.djvu/804

 G L A

G L A

Reiud Glands, glandule r males — Mr. du Vernoy remarks the glandules renales to be very variable m their magnitude, figure, &fc. but that they are always contiguous, and firmly connected to the kidneys. In fome foetus's they appear folid, without any cavity, in others, they are diftended with thin blood ; in adults, they are always flat : they are readily diftended, by blowing air into them by their vein. When the glands are opened, and quickfilver is injected, a great many ducts are feen, at which the mercury runs out. Two arteries and a vein belong to each gland, and a great many duels, like rays, make a circle round it. An artery arifmg from the aorta, is fent down from the lower edge of the gland to the teftes of men, and ovaria of women, which Valfalva miftook for dudts. Comment. Acad. Petrop. torn. 5. GLANIS, in zoology, the name of a fifth, called in Englifh the meat fifth, and in Latin, filurus. AUrovand. de Pifc. 1. 5. c. 25. See the article Silurus. GLANS Marinus, in natural hiftory, a name given to a genus of fhell fifth, more ufually called balanus, and inEnglifh the center fhell. Glans (Cycl.) — Glans Penis. We read of a glans penis regenerated after amputation in the medical Eff. Edinb. vol. 5. art. 35. Glans Trochitifera, in natural hiftory, a name given by Gefncr, and fome other writers, to a kind of figured foffil, found ufually among thetrochitas and entrochi, and evidently appearing to have in fome manner belonged to them. All the writers who have themfelves examined the places where the trochitae are found, have mentioned thefe under the names of glandes trochitifera, others under lefs determinate ones. Agricola calls them lapides informes ; and Lifter after hirn rude ftones, having impremons of the entrochi. Thefe Hones are found bedded in clay or marble among the entrochi ; they are ufually of the bignefs of a middle-fized Walnut, and have the impreffions of entrochi in many places upon their furfaces in confiderable number, fo that the tro- cbita; and entrochi in general feem to have grown from thefe, and thofe who make the trochita? a kind of rock plants, generally efteemed thefe to be the bulbous roots of them. On cleaning thefe ftones with vinegar the im- preffions appear more fair on them ; they are round holes radiated, and exactly refemble the holes in the main ftones of the entrochi, out of which the fmaller branches have been broke. The greater number of thefe glandes or roots of the entrochi are lo fhattered and broken, that they may very Well be called lapides informes, or rude ftones ; but this is not the cafe with them all, for they are fometimes found perfect and uninjured, and are then very elegant and regular bodies. Gefncr de FoJT.

Some of them are of the exact fhapeof a pine apple, or cone, with a hollow bottom, about half an inch deep, and as much over ; on the tops of thefe are found the impremons of fingle entrochi, and round their bottoms, at equal dif- tances, there ftand five Angle feet in figure of a'efcents. Thefe ftones are formed of angular plates : the bottom is compofed of five which are called feet, the middle of five more, all of a fex-angular figure. Others of thefe glandes are found of the fize of a walnut, of the fame fort of conic figure with the other, but the bottom convex. Thefe have alfo at the top generally the figure of one entrochus, and the bottom is edged with five double points, or feet all broken off, and refembling fo many crefcents. This, as well as the other kind, is ufually covered with incruftated fcales or plates, and they refemble nothing more than the fkin of fome of the fifth of the pifcis triangularis kind ; the fkin of the fame fifth, in thefe fpecies, being covered in its feveral parts with fcales of the moft different figures, as trigonal, tetragonal, pen- tagonal, and hexagonal. The angular plates which cover thefe glandes or roots of the entrochi, are often found loofe among the clay, and in the rocks where the entrochi are found. They are of various figures, and many of them ex- tremely elegant, and they are often heaped up together in fuch vaft numbers in the clay, that on warning it vaft multi- tudes are feparated from the fame fmall lump, Agricola de Metall. Phil. Tranf. N 3 100.

The pentagonal ones are fometimes half an inch long and near as much in breadth ; they are convex on the one fide, and concave like a little difti on the other ; on the convex fide there are ufually feveral knots fet in a regular fquare order. Thefe plates grow thin toward the extremities, but very fel- dom form a fharp edge ; fome of thefe are alfo found with but a little convexity on the outfide, and with no hollow at all within : thefe are ufually fmooth all over, and have not the leaft appearance of ever having had any knots, and are very blunt at the edges in fome, but others of them go off fo fine as to be as fharp as a knife. There are fometimes found alfo another kind of thefe, which have one edge indented and the reft plain ; thefe are fmaller than the others, and their convex fide rifes higher, though the concave is not more hollow than in the firft kind : in thefe the indented fide is always the thinneft, and the ftone is always moft floped toward that fide. Some of this laft fort are alfo found channelled on the concave fide in a very regular and orderly manner. Dr. Lifter alfo mentions one very fingular fpeci-

men of this kind, found near Wansford- bridge in North- amptonfhire ; they had one end notched or indented as the others, and the convex part had in the middle a round umbo like fome of the antient fhields, and round about the fides of this a lift of fmaller ftuds.

The fcxangular plates found loofe in the beds of the en- trochi, and which have alfo made part of the coverings of fome of thefe glandes, are ufually fmall ; they are convex on one fide and a little hollowed on the other. The hollow fide is ufually plain, fometimes highly furrowed, but the convex fide is ufually very elegantly wrought with a kind of ftudded and emboffed work. The figures exprcfled by this work are ufually an equilateral triangle, embracing each' corner or angle of the plate, and a fingle right line in the midft, or two triangles one within the other. Another kind of the fexangular plates are fmooth on the convex fide, or only irregularly fcabrous. Thefe are but little hollowed on the under fide, and fome of them are fo thick that they do not deferve the name of plates. The fides of thefe are very un- equal, as the planes in cryftals are ; fometimes there are five large and one fmall plane, fometimes two are broader than the reft, and fometimes more. Thefe are the moft common of all the plates, a thoufand of them being generally found for one of the others. Phil. Tranf. N° 100.

GLANUS, or Glanis, in ichthyology, a name given by Pliny and many other of the old writers to that fpecies of the filurus, which we in England call the {heat fifh, the glanus and filurus, of authors, difti nguifhed by Artedi by the name of the filurus, with four beards on the chin. See the article Silurus.

GLAREANA, in zoology, the name of a bird described by Gefner from a figure, and fufpected to be no way different from the fpipoletta, called tordino by the Venetians, a kind of lark. See Spipoletta.

GLASS {Cycl.) — A glafs much harder than any prepared in the common way, may be made by means of borax in the following method : take four ounces of borax, and an ounce of fine fand ; reduce both to a fubtile powder, and melt them together in a large clofe crucible fet in a wind furnace, keeping up a ftrong fire for half an hour ; then take out the crucible, and when cold break it, and there will be found at the bottom a pure hard glafs, capable of cutting common glafs like a diamond. This experiment, duly varied, may lead to feveral ufeful improvements in the arts of glafs, enamels, and factitious gems, and fhews an expeditious method of making glafs, without any fixed alkali, which has been generally thought an efiential ingredient in glafs, and it is not yet known whether calcined cryftal, or other fubftances, being added to this fait inftead of fand, it might not make a glafs approaching to the nature of a diamond. Shaw's Lectures, p. 426.

Annealing of Gl ass — The operation of annealing of glafs is performed in a peculiar furnace called the leer which confifts of two parts, the tozucr and the leer. The yeflels as foon as made, are placed by the fervitors on the floor of the former, to anneal ; which done, they are drawn fluwly in a fort of pan called fracbes, by an operator called the farole-inan, all along the leer, the fpace of five or fix yards, to give'' them time to cool gradually ; fo that when they reach the mouth of the leer, they are found quite cold a.

The particles of glaf by annealing are fuppofed to lofe part of their fpringinefs, and their brittlenels at the fame time. A gradual heating or cooling, of glnfs, according to Dr. Hook, anneals or reduces its parts to a texture more loofe, and eafy to be broke ; but withal more flexible than before ". And hence in fome meafure the phsenomena of glafs drops. [ — 3 Merret, Not. to Neri, p. 243. feq. b Hook, Microgr. obf. 7. p. 37. — ]

Borrichius, in his chymiftry, feemsto think that the render- ings/a/} ductile or malleable, is not fo impracticable as it is ufually thought ; in fupport of this, he alledges the in- ftance of the luna cornea, which is a fort of fait made of filver diflblved in an acid, and which is in fome degree ductile, and fo far altered from the nature of filver that it may be melted at a candle, and reduced into fmall tranlparent leaves ; and adding to this the procefs for making a ductile fait out of common fal armoniac, difiolved in a large glafs and cryftal- lized a vaft many times j the cryftals of this fait, he fays, at laft became half a foot long, and were flexile and elaftic, and in fome degree ductile under a hammer. From thefe changes in bodies naturally brittle as falts are, he judges, that the fame changes may be made in glafs. Phil. Tranf. N° 30.

Glajfes unannealed, are fo excefiively brittle, as to fly and break of themfelves, even frequently before they are well cold. Hence, the practice of nealing or annealing was de- vifed.

Some of the phenomena depending on the fragility of un- annealed glaf deferve the attention of the curious. Thofe of the lacrymae, or glafs drops, were among the firft taken notice of; and it has alfo been obferved, that hollow bells made of unnealed glafs, with a fmall hole in them, will fly to pieces, by the heat of the hand only, if the hole by which the internal and external air communicate be flopped with a finger. Phil. Tranf. N J 477. Sect. 3.

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