Imágenes de páginas
PDF

reference; and the whole are circumscribed by well-designed figures of the constellations, faintly engraved.

The great circles are divided into twenty minutes of a degree, and the equinoctial in addition into two minutes of time, so that, by estimation, the solution of problems may be obtained to five minutes of a degree, or half a minute of time; a degree of accuracy sufficiently useful not only for all the common problems, but most of the trigonometrical ones.

As the reading off of time is found to be a ready and convenient method by hour circles attached to the meridians, the horary circle has been contrived to admit of being slid away from its pole, upon the exterior edge of the meridian; this is done by making the extremity of the pole, which carries the index of the horary circle, moveable by unscrewing. The horary circle being attached to the meridian barely by springs, when the index is unscrewed, the circle may consequently be slid to any part of the meridian. This contrivance is necessary only for the circle of the north pole of Messrs. W. and S. Jones's terrestrial globe, who have adopted this circle, and at the south pole of the globes have applied the interior brass index, or circles abovementioned.

Plates for the British globes of twelve inches diameter, have been reduced and abridged, from the eighteen inches abovementioned. Plates for globes of nine, twelve, and twenty-one inches diameter, have been engraved by Mr. Cary, of the Strand. The stars of his celestial globe are not circumscribed with the figures of the constellations.

GLOBULAR chart, a name given to the representation of the surface, or of some part of the surface of the terrestrial globe upon a plane, wherein the parallels of latitude are circles nearly concentric, the meridians curves bending towards the poles, i and the rhomb-lines are also curves.

Globular Mailing. See Sailing.

GLOBULARIA, in botany, a genus of the Tetrandria Monogynia class and order. Natural order of Aggregate. Lysimachix, Jussieu. Essential character: calyx common, imbricate; proper tubular inferior; corollets the upper lip, two-parted; lower three-parted; receptacle chaffy. There are eight species.

GLORIOSA, in botany, a genus of the Hexandria Monogynia class and order. Natural order of Sarmentacen. Lilia, Jus

sieu. Essential character: corolla six-petalled, waved, reflex ; style oblique. There are two species, ri:. G. superba, superb lily, and G. simplex.

GLOSS, in matters of literature, denotes an exposition or explication of the text of any author, whether in the same language, or any other; in which sense it differs little from commentary.

GLOSSOMA, in botany, a genus of the Tetrandria Monogynia class and order. Natural order of Rhamni, Jussieu. Essential character: calyx turbinate four-toothed, superior; corolla four-petalied; anthers almost united, with a membranaceous scale. at the end; stigmas four, drupe. There is only one species, viz. G. guianensis, a native of Guiana, flowering in September. Votomita is the vernacular name.

GLOSSOPETALUM, in botany, a s-enus of the Pentandria Pentagynia class and order. Natural order of Rhamni, Jussieu. Essential character: calyx very small, fivetoothed ; petals five, with a strap at the tip of each; berry. There are two species, both lofty trees, natives of Guiana and Cayenne.

GLOTTIS, in anatomy, the mouth or aperture of the larynx, through which the air ascends and descends in respiring. It can be dilated or contracted at pleasure, and by the various vibratory motions of which the tones of the voice are modified. The name was applied by the ancients to an additional moveable part of the flute, which they placed between their lips in performance, and which is supposed to have been similar to our reed. GLOW worm. See Lampyris. GLOXINIA, in botany, so called in honour of Ben. Petr. Gloxin, of Colmar, a genus of the Didynamia Angiospermia class and order. Natural order of Personatae. Campanulacex, Jussieu. Essential character: calyx superior, five-leaved; corolla bell-shaped, with the border oblique; filaments, with the rudiment of a fifth, inserted into the receptacle. There is only one species, viz. G. maculata, spotted gloxinia, a native of South America.

GLUCINA, in chemistry, an earth lately discovered by Vauquelin, while he was analizing the beryl, to ascertain whether its constituent parts were the same as those of the emerald. See Beryl. In this experiment he found the glucina, which he so named from its sweetish kind of taste. Glucina, in the form of powder, or in fragments, is almost three tunes as heavy a* water; it is infusible in the fire; it does not contract, like alumina, by great heat, and it has no effect on vegetable colours. The oxygen, nitrogen, and hydrogen gases have no action on it; nor is it acted upon by carbon, sulphur, or phosphorus. It combines with sulphurated hydrogen. It is insoluble in water, but combines with acids, making with them soluble salts, distinguished by a sweet and slightly astringent taste.

GLUE, among artificers, a tenaceous viscid matter, which serves as a cement to bind or connect things together. Glues are of different kinds, according to the various uses they are designed for, as the common glue, glove glue, parchment glue, isinglass glue, &c

The common or strong glue is chiefly used by carpenters, joiners, cabinet-makers, &c. and the best kind is that made in England, in square pieces of a ruddy brown colour, and next to this the Flanders glue. It is made of the skins of animals, as oxen, cows, calves, sheep, &c, and the older the creature is, the better is the glue made of its hide. Indeed, whole skins are but rarely used for this purpose, but only the shavings, parings, or scraps of them; or the feet, sinews, &c. That made of whole skins, however, is undoubtedly the best; as that made of sinews is the very worst.

In making glue of parings, they first steep them two or three days in water; then washing them well out, they boil them to the consistence of a thick jelly, which they pass, while hot, through ozier baskets, to separate the impurities from it, and then let stand some time, to purify it further: when all the filth and ordures are settled to the bottom of the vessel, they melt and boil it a second time. They next pour it into flat frames or moulds, whence it is taken out pretty hard and solid, and cut into square pieces or cakes. They afterwards dry it in the wind, in a sort of coarse net; and at last string it, to finish its drying. The glue made of sinews, feet, &c. is managed after the same manner; only with this difference, that they bone and scour the feet, and do not lay them to steep. The best glue is that which is oldest - and the surest way to try its goodness, is to lay a piece to steep three or four days, and if it swell considerably without melting, and when taken out resumes its former dryness, it is excellent. A glue that will hold against fire or water may be made thus: mix a handful of quick lime with four ounces of linseed pi), boil them to a good thickness,

then spread it on tin plates in the shade, and it will become exceedingly hard, but may be dissolved over a fire, as glue, and will effect the business to admiration.

Glue, method of preparing and using. Set a quart of water on the fire, then put in about half a pound of good glue, and boil them gently together till the glue be entirely dissolved, and of a due consistence. When glue is to be used, it must be made thoroughly hot; after which, with a brush dipped in it, besmear the faces of the joints as quick as possible; then clapping them together, slide or rub them lengthwise one upon another, two or three times, to settle them close; and so let them stand till they are dry and firm.

Glue, parchment, is made by boiling gently shreds of parchment in water, in the proportion of one pound of the former to six quarts of the latter, till it be reduced to one quart. The fluid is then to be strained from the dregs, and afterwards boiled to' the consistency of glue. Isinglass glue is made in the same way ; but this is improved by dissolving the isinglass in alcohol, by means of a gentle heat. See Cements.

GLUME See Botany.

GLUTA, in botany, a genus of the Pentandria Monogynia class and order. Essential character: calyx bell-shaped, deciduous; petals five, glued at bottom to the column of the germ; filaments inserted into the tip of the column; germ sitting on an oblong column. There is only one species, viz. G. ben'ghas, a native of Java.

GLUTEN. With the fecula and saccharine matter which compose the principal part of nutritive grain, is another substance approaching more nearly in its characters to animal matter than any other product of the vegetable system. From the resemblance in its properties to the animal principle formerly called gluten, but now described under the term Fibrin (which see) it has received the name of vegetable gluten. It is obtained in largest quantities from wheat, amounting to the twelfth part of the whole grain, by kneading the flour into paste, which is to be washed very cautiously, by kneading it under a jet of water, till the water carries off nothing more, but runs off colourless, what remains is gluten: it is ductile and elastic; it has some resemblance to animal tendon or membrane; it is very tenacious, and may be used as a cement for broken porcelain vessels. It has a peculiar smell, with scarcely any taste. When exposed to the air it annine* a brown colour, and becomes apparently covered with a coat of oil. When completely dry it resembles glue, and breaks like glass. It is insoluble in water, alcohol, and ether; but the acids dissolve it, and the alkalies precipitate it It has a strong affinity for the colouring matter of vegetables, and likewise for resinous substances. When kept moist it ferments, and emits a very offensive smell; the vapour blackens silver and lead. Its constituent parts are oxygen, hydrogen, carbon, and azote. It exists, as we have observed, most abundantly in wheat, but it is found in large quantities in many other plants. It is gluten that renders wheat so useful in the art of bread making.

GLYCINE, in botany, a genus of the Diadelphia Decandria class and order. Natural order of Pal .ilionaceae, or Leguminosx. Essential character: calyx two-lipped ; corolla the keel turning back the banner at the tip. There are twenty-five species.

GLYCYRRHIZA, in botany, English liqvorice, a genus of the Diadelphia Decandria class and order. Natural order of Papilionaces, or Legnminosse. Essential character: calyx two-lipped, upper lip threeparted, lower undivided; legume ovate, compressed. There are four species. These are tall growing perennial, herbaceous plants, with the stalks somewhat woody at bottom. The stipules are distinct from the petiole; the flowers in a head or spike from the axils and at the ends of the branches; seed vessel a legume or pod, smooth, hairy, or prickly.

GLYPH, in sculpture and architecture, denotes any canal or cavity, used as an ornament.

GLYSTER, or Clyster among physicians. See Clyster.

GMELINA, in botany, so called in honour of Joh. George Gmelin, professor of natural history at St. Petersburgh, afterwards of Botany at Tubingen, a genus of the Didynamia Angiospermia class and order. Natural order of Personate. Vitices, Jussien. Essential character: calyx slightly four-toothed; corolla four-cleft, bell-shaped; anthers two-parted, two-simple; drupe with a two or three-celled nut. Then is but one species, riz. G. asiatica.

GNAPHALIUM, in botany, a genus of the Syngcnesia Polygamia Superfiua class and order. Natural order of Composite Discoidea*. Corymbiferx, Jiissieu. Essential character: calyx imbricate, with the marginal scales rounded, scariosc, coloured;

down feathered; receptacle naked. There are sixty-six species: the numerous species of this genus are chiefly under shrubs or herbs; the leaves are alternately placed, generally hoary; the flowers usually terminate the stem and branches in globes or corymbs. The calyx is permanent with yellow or white scales.

GNAT. See Cdlex.

GNEISS, in mineralogy, is composed principally of felspar, quartz, and mica, forming plates, laid on each other, and separated by thin layers of mica. It differs from granite by being shistose ; though, like that, it sometimes contains short and garnet The beds of gueiss sometimes alternate with layers of granular limestone, shistose, hornblende, and porphyry. It is rich in ores, almost every metal has been found in gneiss rocks, either in veins or beds. Mr. Jameson mentions four kinds of gneiss: 1. That which approaches to the granular structure. 2. The waved or undulated. 3. The common; and, 4. The thin slaty; and he says the order of their transition is also that of their relative antiquity, consequently the more granular the structure, the older the rock; and, on the contrary, the more slaty, the newer it is. In the last member of the series is the smallest portion of felspar, and largest of mica; hence its texture is more completely slaty than that of any of the others. The other extremity contains much felspar, and but little mica. The common contains a nearly equal quantity of felspar and quartz.

GNETUM, in botany, a genus of the Monoecia Monadelphia class and order. Natural order of Piperita;. / Urticae, Jussien. Essential character: male, an ancient with scales; corolla none; filaments one, with two anthers: female, an ancient with scales; corolla none; style with a bifid stigma; drupe with one seed. There is only one species, viz. G. gnemon, a native of the East Indies, where the leaves, male catkins and fruits are eaten.

ON 11)1 A, in botany, a genus of the Octandria Monogynia class and order. Natural order of Veprecula-. Thymelayr, Juslien. Essential character: calyx funnelform, four-cleft; petals four, inserted into the calyx; seed one, somewhat berried. There are eleven species.

GNOMON, in dialling, the stile, pin, or cock of a dial; which, by its shadow, shows the hour of the day. The gnomon of every dial represents the axis of the world. Scf Dial and Dialing.

Gnomon, in geometry. If, m a parallelogram (PL VI. Misccl. fig. 1.) the diameter, A C, be drawn; also two lines, E F, HI, parallel to the sides of the parallelogram, and cutting the diameter in one and the same point, G, so that the parallelogram is, by these parallels, divided into four parallelograms, then are the two parallelograms, DG, HO, through which the diameter does not pass, called complements; those through which the diameters pass, E H, F I, are called the parallelograms about the diameter; and a gnomon consists of the two complements, and either of the parallelograms about the diameter, tit.' G D + HE + EI, orGD + FI-f GB

Gnomon, in astronomy, a stile erected perpendicular to the horizon, in order to tind the altitude of the sun. Titus, in the right angled triangle ABC, fig. 2, are given, A B, the length of the stile, B C, the length of its shadow, and the right angle, A B C. Hence, making, C B, the radius, we have this analogy for finding the angle, A C B, the sun's altitude, ctz. B C: A B :: radius: tangent of the angle C.

By means of a gnomon, the sun's meridian altitude, and consequently the latitude of the place, may be found more exactly than with the smaller quadrants.

By the same instrument, the height of any object, G H, may be found ; for as, U F, fig. 5, the distance of the observer's eye from the gnomes, is to, D E, the height of the stile, so is, F H, the distance of the observer's eye from the object to, G H, its height.

The gnomon may be made useful in taking the meridian altitude of the sun, and' thence finding the latitude of the place. Having a meridian line drawn through the centre of the gnomon, mark the point where the shadow of the gnomon terminates when projected along the meridian line, and measure the distance of that point from the centre of the gnomon, which will be the length of its shadow ; then having the height of the gnomon, and the length of the shadow, the Sun's altitude is easily found. Thus, if A B be the gnomon, and A C the length of the shadow, then in the right angled triangle, ABC, we have A B and B C given; hence the angle C is easily found, for CB: B A :: radius: lauztnt of the angle C ; that is, as the length of the shadow is to the height of the gnomon, so is radius to the tangent of the sun's altitude above the horizon. Ex. We learn from Pliny, at the three of the equinoxes, that the shadow

was to the gnomon as 8:9, therefore we say as 8; 9 :: R: ■' = 1.125 the tangent of an angle of 48° 22', which is the height of the equator at Rome, and its complement 41° 38' is therefore the height of the pole, or the latitude of the place. This method, however, requires correction for the sun's parallax, and for refraction.

GNOMONICS, the art of Dialing, which see. From the shadow of a rod, perpendicularly or obliquely placed on a plane, may be determined a triangle, by drawing from the top of the rod it line that shall touch the luminous body, forming with the rod the least possible angle. The sides of the triangle will be, first, the part of this line comprehended between the top of the rod and the given plane; then the rod. itself, and lastly, the line drawn from the bottom of the rod till it meets the other line already mentioned. This last line will be the shadow relatively to the given plane: it will increase and decrease in proportion as the sine of the angle, whose summit coincides with the summit of the rod, shall be greater or less, that is, in proportion as the luminous body shall descend or ascend with respect to the given plane; and if that body move to the right or the left of the position first occupied by the triangle, that determines the shadow, which will move on the plane in a contrary direction; and on these principles the art of dialing consists. . GNOSTICS, in church history, a sect of Christians so called from their pretensions to be more enlightened than others, and from their affecting to be able to bring back mankind to the knowledge of the true God. The opinions held by these people have not been completely ascertained; they were fond of speculation, and like many of the gnostics of modern times, held public worship and positive institutions in little esteem.

GOAL, or Gaol. See Gaol.

GOAT, in zoology. See Capra. These animals require scarcely any thing to keep them. Their milk is esteemed the greatest nouiisher of all liquids, women's milk excepted, and very comfortable to the stomach. The young kids also are very good for the table, and may be managed in all respects like lambs.

Goat's beard, in botany. See TbaooPocon.

Goat sucker. Sec Caprinulgus. These birds are regarded by the American Indians as very ominous. They believe that goat-suckers were not known in their country till the English had made depredation upon it, and that they are, in fact, the departed spirits of the murdered Indians. In Carolina the lower class of people look upon them as birds of ill omen, and are gloomy and almost melancholy if one alights on the house or near the door, and begins its call, which they will sometimes do, even on the very threshold, imagining that it is a sure prognostic of the death of one of the family,

GOBIUS, the goby, in natural history, a genus of fishes of the order Thoracici. Generic character: head small; eyes approximated, with two punctures between them; gill membrane, four-rayed; ventral fins, united into a funnel-like oval; dorsal fins two. There are twenty-five species, of which we shall notice the following, G. niger, or the black goby, is about six inches in length. It inhabits the Mediterranean and North Seas, and often, in summer, when it deposits its spawn enters the mouths of rivers for that purpose. It is eaten, but not highly valued. The ventral fins unite into a species of funnel, by which this fish is said often to attach itself almost inseparably to stones and rocks. It lies chiefly under stones; and its food consists of worms, insects, and the young of small fishes. For another species, the lanceolated goby, see Pisces, Plate IV. fig. 4.

GOD, Deu.t, the Supreme Being, the first cause or creator of the universe, and the only true object of religious worship. The Hebrews called him Jehovah ; which name they never pronounced, but used instead of it the words Adonai, or Elohim.

God, says Sir Isaac Newton, is a relative term, and has respect to servants. It denotes, indeed, an eternal, infinite, absolutely perfect being: but such a being without dominion, would not be God. The word God frequently signifies lord, but every lord is not God. The dominion of a spiritual being, or lord, constitutes God; true dominion, true God. From such true dominion it follows that the true God is living, intelligent, and powerful; and from his other perfections, that he is supreme, or supremely perfect. He is eternal and infinite; omnipotent and omniscient; that is, he endure, from eternity to eternity, and is present from infinity to infinity. He governs all things that exist, and knows all things that are to be known. He is not eternity or infinity, but eternal and infinite. He is not duration and space, but he endures and is present; he endures always, and is present every where; and by existing always and

every where, constitutes the very things we call duration and space, eternity and infinity. He is omnipresent, not only virtually, but substantially; for power without substance cannot subsist. All tilings are contained and move in him, but without any mutual passion; that is, he suffers nothing from the motions of bodies, nor do they undergo any resistance from his omnipresence.

It is confessed, that God exists necessarily; and by the same necessity he exists always and every where. Hence also he must be perfectly similar; all'eye, all ear, all brain, all arm, all perception, intelligence, and action; but after a manner no t at all corporeal, not at all like men; after a manner altogether unknown to us. He is destitute of all body and bodily shape, and therefore cannot be seen, heard, or touch ed; nor ought to be worshipped under the representation of any thing corporeal. We know him only by his properties, or attributes, by the most wise and excellent structure of things, and by final causes: but we adore and worship him only on account of his dominion; for God setting aside dominion, providence, and final causes, is nothing but fate and nature.

The plain argument, says Mr. Maclaurin, for the existence of the deity, obvious to all, and carrying irresistible conviction with it, is from the evident contrivance and fitness of things for one another, which we meet with throughout all parts of the universe. There is no need of nice or subtle reasonings in this matter; a manifest contrivance immediately suggests a contriver. It strikes us like a sensation, and artful reasonings against it may puzzle us, but without shaking our belief. No person, for example, that knows the principles of optics and the structure of the eye, can believe that it was formed without skill in that science, or that the ear was formed without the knowledge of sounds, or that the male and female, in animals, were not formed for each other, and for continuing the species. All our accounts of nature are full of instances of this kind. The admirable and beautiful structure of things for final causes, exalt our idea of the contriver: the unity of design shows him to be one. The great motions in the system, performed with the same facility as the least, suggest his almighty power, which gave motion to the earth and the celestial bodies with equal ease as to the minutest particles. The subtilty of the motions and actions in the internal parts of bodies, shows that his influence penetrates the iu •

« AnteriorContinuar »