ripen in autumn. S. indicum, with trifid lower leaves, grows naturally in India; this is also an annual plant; the stalk rises taller than that of the former; the lower leaves are cut into three parts, which is the only difference between them. The first sort is frequently cultivated in all the eastern countries, and also in Africa, as a pulse; and of late years the seeds have been introduced into Carolina by the African negroes, where they succeed extremely well. The inhabitants of that country make an oil from the seed, which will keep good for many years, without having any rancid smell or taste, but in two years become quite mild; so that when the warm taste of the seed, which is in the oil when first drawn, is worn off, they use it as a salad-oil, and for all the purposes of sweet oil. The seeds of this plant are also used by the negroes for food; which seeds they parch over the fire, and then mix them with water, and stew other ingredients with them, which makes a hearty food.

SESELI, in botany, meadow saxifrage, a genus of the Pentandria Digynia class and order. Natural order of Umbellatæ or Umbelliferæ. Essential character: umbels globular; involucre of one or two leaflets; fruit ovate, striated. There are fifteen species.

fore, is never allowed in actions upon the case, trespass, replevin, &c.; nor of a penalty in debt on bond conditioned for the performance of covenants, &c.; nor of general damages in covenant or assumpsit: but where a bond is conditioned for the pay. ment of an annuity, a set off may be allowéd. A debt barred by the statute of limitations cannot be set off; and if it be pleaded in bar to the action, the plaintiff may reply the statute of limitations; or if given in evidence, on a notice of set off, which is one mode of setting up this sort of counter-demand, it may be objected to at the trial.

SET, or SETS, a term used by the farmers and gardeners to express the young plants of the white thorn and other shrubs, with which they use to raise their quick or quickset hedges.

SETON, in surgery, a few horse hairs, small threads, or large packthread drawn through the skin, chiefly the neck, by means of a large needle or probe, with a view to restore or preserve health.

SETTE, a vessel very common in the Mediterranean, with one deck, and a very long and sharp prow: they carry some two masts, some three, without top-masts. Their yards and sails are all like the mizen; the least of them are of sixty tons burden.

SESUVIUM, in botany, a genus of the Icosandria Trigynia class and order. Natural order of Succulenta. Ficoidæ, Jussieu. Essential character: calyx five-parted, coloured; petals none; capsule ovate, three-celled, cut round, many-seeded. There is only one species, riz. S. portulacastrum, a native of the West Indies.

SET off, in law, is when the defendant acknowledges the justice of the plaintiff's demand on the one hand, but on the other sets up a demand of his own, to counterbalance that of the plaintiff, either in the whole or in part; as if the plaintiff sue for 101. due on a note of hand, the defendant may set off 91. due to himself for merchandize sold to the plaintiff, or for any other demand, the amount of which is ascertained in damages.

The action in which a set off is allowable upon the statutes 2 and 3 George II. c. 22 and 24, are debt, covenant, and assumpsit, for the non-payment of money; and the demand intended to be set off must be such as might have been made the subject of one or other of these actions. A set off, there

sion for ships of war, and the like.

SETTING, in astronomy, the withdrawing of a star or planet, or its sinking below the horizon. Astronomers and poets make three different kinds of setting of the stars, viz. the cosmical, acronychal, and helical.

SETTING, in the sea language. To set the land or the sun, by the compass, is to observe how the land bears on any point of the compass, or on what point of the compass the sun is. Also, when two ships sail in sight of one another, to mark on what point the chased bears, is termed setting the chase by the compass.

SEWER, in the household, an officer who comes in before the meat of a king or nobleman, to place and range it on the table.

SEWER is also a passage or gutter made to carry water into the sea or a river, whereby to preserve the land, &c. from inundations and other annoyances. The business of the commissioners of sewers, or their office in particular, is to repair seabanks and walls, survey rivers, public streams, ditches, &c. and to make orders for that purpose. These commission

ers have, likewise authority to make inquiry of all nuisances or offences committed by the stopping of rivers, erecting mills, not repairing banks, bridges, &c. and to tax persons chargeable for the amending of defaults that tend to the obstruction or hindrance of the free passage of the water through its ancient courses. They may not only make a rate and assessment for repairs, but also may decree lands to be sold, in order to levy charges assessed upon nonpayment thereof, &c. But the decrees of the commissioners are to be certified in Chancery, and have the King's assent to be binding, and their proceedings are subject to the jurisdiction of the King's Bench, In the making of a rate or tax, the commissioners are to assess every owner or possessor of lands in danger of receiving any damage by the waters, equally according to the quality of their lands, rents, and numbers of acres, and their respective portions and profits, whether it be of pasture, fishing, &c. And where no persons or lands can be known that are liable to make repairs of banks and sewers, then the commissioners are to rate the whole level. The 3 James I. ordains that all ditches, banks, bridges, and water-houses, within two miles of London, adjoining to, and falling into the Thames, shall be subject to the commissioners of sewers. Also the Lord Mayor, &c. may appoint persons in that case to have the power of commissioners of sewers. Persons breaking down sea-banks, whereby lands are damaged, are adjudged to be guilty of felony; and removing piles, &c. forfeit 201. by 6 and 10 George II. c. 32.

SEX, something in the body which distinguishes male from female.

SEXAGENARY, something relating to the number sixty. Thus, sexagenary, or sexagesimal arithmetic, is a method of com. putation proceeding by sixties; such is that used in the division of a degree into sixty minutes, of the minute into sixty seconds, of the second into sixty thirds, &c. Also sexagenary tables are tables of proportional parts, showing the product of two sexagenaries that are to be multiplied, or the quotient of the two that are to be divided.

SEXAGESIMALS, or SEXAGESIMAL fractions, fractions whose denominators proceed in a sexagecuple ratio; that is, a prime, or the first minute =; a second a third=118000.

Anciently there were no other than sexagesimals used in astronomy, and they gre still retained in many cases, though deci.

mal arithmetic has now grown into use in astronomical calculations. In these fractions, which some call astronomical frac tions, the denominator being always sixty, or a multiple thereof, is usually omitted, and the numerator only written down, thus, 4o, 59′, 32′′, 50′′, 16", is to be read four degrees, fifty-nine minutes, thirty-two seconds, fifty thirds, sixteen fourths, &c.

SEXANGLE, in geometry, a figure having six sides, and consequently six angles.

SEXTANS, a sixth part of certain things. The Romans having divided their as into twelve ounces, or unica, the sixth part of that, or two ounces, was the sextans. Sextans was also a measure which contained two ounces of liquor, or two cyathi.

SEXTANT, in mathematics, denotes the sixth part of a circle, or an arch comprehending sixty degrees. The word sextant is more particularly used for an astronomical instrument made like a quadrant, excepting that its limb only comprehends sixty degrees. The use and application of the sextant is the same with that of the quadrant. See QUADRant.

SEXTILE, the position or aspect of two planets when at sixty degrees distance, or at the distance of two signs from one an other. It is marked thus ( * ).

SEXTON, a church officer, whose busi ness is to take care of the vessels, vestments, &c. belonging to the church, and to attend the minister, churchwardens, &c. at church. He is usually chosen by the parson only. The office of sexton, in the Pope's chapel, is appropriated to the order of the hermits of St. Augustine. He is generally a bishop, though sometimes the Pope only gives a bishopric in particular to him on whom he confers the post: he takes the title of prefect of the Pope's sacristy, and has the keeping of the vessels of gold and silver, the relics, &c. When the pope says mass, the sexton always tastes the bread and wine first. If it be in private he says mass, his Holiness of two wafers gives him one to eat; and if in public, the cardinal who assists the Pope in quality of deacon, of three wafers gives him one to eat. When the Pope is very sick, he administers to him the sacrament of extreme unction, &c. and enters the conclave in quality of first conclavist.

SEXUAL system, in botany, that system of classification which was invented, by the immortal Linnæus, professor of physic and botany, at Upsal, in Sweden. It is founded on the parts of fructification, viz. the stą.

mens and pistils; these having been observed with more accuracy since the discovery of the uses for which nature has assigned them, a new set of principles have been derived from them, by means of which the distribution of plants has been brought to a greater precision, and rendered more conformable to true philosophy, in this system, than in any one of those which preceded it. The author does not pretend to call it a natural system, he gives it as artificial only, and modestly owns his inability to detect the order pursued by nature in her vegetable productions; but of this he seems confident, that no natural order can ever be framed without taking in the materials out of which he has raised his own; and urges the necessity of admitting artificial systems for convenience, till one truly natural shall appear. Linnæus has given us his "Fragmenti Methodi Naturalis," in which he has made a distribution of plants under various orders, putting together in each such as appear to have a natural affinity to each other; this, after a long and fruitless search after the natural method, he gives as the result of his own speculation, for the assistance of such as may engage in the same pursuit hereafter. Not finding it practicable to form a system after the natural method, Linnæus was more fully convinced of the absolute necessity of adopting an artificial one, of which a detailed account is given under the article BOTANY.

SHAD, in ichthyology, a species of Clupea, with the upper jaw bifid at the extremity, and spotted with black; it greatly resembles the common herring, and is, on that account, sometimes called the mother of herring; all the fins are whitish, except that on the back; the tail is very much forked.

SHADOW, in optics, a privation or di minution of light, by the interposition of an opaque body; or it is a plane where the light is either altogether obstructed, or greatly weakened, by the interposition of some opaque body between it and the luminary. A shadow of itself is invisible; and therefore, when we say we see a shadow, we partly mean that we see bodies placed in the shadow, and illuminated by light reflected from collateral bodies; and, partly, that we see the confines of the light. If the opaque body that projects the shadow be perpendicular to the horizon, and the place it is projected on be horizontal, the shadow is called a right shadow; and such are the shadows of men, trees, buildings,

mountains, &c. But if the opaque body be placed parallel to the horizon, the sha dow is called a versed shadow; as the arms of a man stretched out, &c.

"The laws of the projection of Shadows from opaque bodies." 1. Every opaque body projects a shadow in the same direction with its rays; that is, towards the part opposite to the light. Hence, as either the luminary or the body changes place, the shadow likewise changes. 2. Every opaque body projects as many shadows as there are luminaries to enlighten it. 3. As the light of the luminary is more intense, the shadow is the deeper: hence the intensity of the shadow is measured by the degrees of light that space is deprived of. 4. If a luminous sphere be equal to an opaque one it illuminates, the shadow, which this latter projects, will be a cylinder, and consequently will be propagated still equal to itself, to whatever distance the luminary is capable of acting, so that if it be cut in any place, the plane of the section will be a circle, equal to a great circle of the opaque sphere. 5. If the luminous sphere be greater than the opaque one, the shadow will be conical. If, therefore, the shadow be cut by a plane, parallel to the base, the plane of section will be a circle; and that so much the less as it is a greater distance from the base. 6. If the luminous sphere be less than an opaque one, the shadow will be a truncated cone; and, consequently, grows still wider and wider; and therefore, if cut by a plane parallel to the section, that plane will be a circle, so much the greater as it is further from the base.

The sun being vastly larger than the whole globe of the earth must give all its shadows pointed, by reason that it illumines more than half of them. In consequence of this demonstration we might conclude, that all the sun's shadows must be less than the bodies that project them, and diminished more and more as they recede further and further. Now this would be true were there any relation between the body illuminated and the body illumining; but as all objects on the earth are so small in comparison of that star, the diminution of their shadows is imperceptible to the eye, which sees them always equal; i. e. either broader or narrower than the body that forms them: on this account all the shadows caused by the sun are made in parallels. From the whole it appears, that to find the shadow of any body whatever

opposed to the sun, a line must be drawn from the top of the luminary perpendicular to the place where the foot of the luminary is to be taken: and through this place an occult line is to be drawn through one of the angles of the plan of the object, and another from the sun to the same angle; and the intersection of the two lines will show how far the shadow is to go: all the other lines must be drawn parallel hereto. The shadows of the sun are equal in objects of the same height, though at a distance from each other. Experience teaches, that stiles, or elevations of the same height, removed 'to a distance from each other, do yet project equal shadows at the same time: for they are lengthening and shortening, in proportion as the sun comes nearer, or recedes further off; one or other of which he is continually doing.

SHADOW, in geography. The inhabitants of the terraqueous globe of the earth receive different denominations, according to the different ways wherein their shadows are projected; as ascii, amphiscii, heteroscii, and periscii.

SHADOW, in painting, an imitation of a real shadow, effected by gradually heightening and darkening the colours of such figures as by their dispositions cannot receive any direct rays from the luminary that is supposed to enlighten the piece. The management of the shadows and lights makes what the painters call claro-obscuro.

SHAFT of a column, in building, is the body thereof between the base and capital: so called from its straightness. The term shaft is also used for the spire of a church steeple, and for the tunnel of a chimney. See ARCHITEcture.

SHAFT, in mining, is the pit or hollow entrance into the mine.

SHAGREEN, or CHAGREEN, in commerce, a kind of grained leather, prepared, as is supposed, of the skin of a species of squalus, or hound-fish, called the shagree, or shagrain, and much used in covering cases, books, &c. It is imported from Constantinople, Tauris, Tripoli, Algiers, and from some parts of Poland, where it is prepared in the following manner: the skin being stretched out, is first covered over with mustard seed, which is bruised upon it: and being thus exposed to the weather for some days, it is then tanned. The best is of a brownish colour, as the white sort is the worst: it is extremely hard; yet, when steeped in water, it becomes soft and pliable; and being

fashioned into case-covers, it readily takes any colour, as red, green, yellow, black, according to the fancy of the workman.

SHAMBLES, among miners, a sort of niches, or landing places, left at such distances in the adits of mines, that the shovelmen may conveniently throw up the ore from shamble to shamble, till it comes to the top of the mine.

SHAMMY, or CHAMOIS Leather, a kind of leather, dressed either in oil or tanned; and much esteemed for its softness, pliancy, and being capable of bearing soap without hurt. The true shammy is prepared of the skin of the chamois-goat. See CAPRA.

The true chamois leather is counterfeited ́with common goat, kid, and even sheepskin; the practice of which makes a particular profession, called by the French chamoisure. The last is the least esteemed, yet so popular, and such vast quantities prepared, especially about Orleans, Marseilles, and Thoulouse, that it may not be amiss to give the method of preparation.

"The manner of chamoising, or of preparing sheep, goat, or kid-skins in oil, in imitation of chamois." The skins being washed, drained, and smeared over with quick-lime on the fleshy side, are folded in two, lengthwise, the wool outwards, and laid on heaps, and so left to ferment eight days; or, if they had been left to dry after flaying, for fifteen days. Then they are washed out, drained, and half-dried, laid on a wooden leg or horse, the wool stripped off with a round staff for the purpose, and laid in a weak pit, the lime whereof had been used before, and had lost the greatest part of its force. After twenty-four hours they are taken out, and left to drain twenty-four more; then put in another strong pit. This done, they are taken out, drained, and put in again by turns; which begins to dispose them to take oil: and this practice they continue for six weeks in summer, or three months in winter; at the end whereof they are washed out, laid on the wooden leg, and the surface of the skin on the wool side peeled off, to render them the softer; then, made into parcels, steeped a night in the river; in winter, more; stretched six or seven over one another, on the wooden leg; and the knife passed strongly on the flesh side, to take off any thing superfluous, and render the skin smooth. Then they are stretched as before, in the river, and the same operation repeated on the wool side; then thrown into a tub of water with bran in it, which is

brewed among the skins till the greatest part stick to them; and then separated into. distinct tubs, till they swell and rise of themselves above the water. By this means the remains of the lime are cleared out they are then wrung out, hung up to dry on ropes, and sent to the mill, with the quantity of oil necessary to scour them: the best oil is that of stock-fish. Here they are first thrown in bundles into the river for twelve hours, then laid in the mill trough, and fulled without oil till they be well softened; then oiled with the hand, one by one, and thus formed into parcels of four skins each, which are milled and dried on chords a second time, then a third; then oiled again and dried.

This process is repeated as often as necessity requires; when done, if there be any moisture remaining, they are dried in a stove, and made up into parcels wrapped up in wool; after some time they are opened to the air, but wrapped up again as before, till such time as the oil seems to have lost all its force, which it ordinarily does in twenty-four hours.

The skins are then returned from the mill to the chamoiser to be scoured; which is done by putting them into a lixivium of wood-ashes, working and beating them in it with poles, and leaving them to steep till the lye have had its effect; then wrung out, steeped in another lixivium, wrung again, and this repeated till all the grease and oil be purged out. They are then half dried, and passed over a sharp-edged iron instru ment, placed perpendicular in a block, which opens, softens, and makes them pliable: lastly, they are thoroughly dried, and passed over the same instrument again, which finishes the preparation, and leaves them in form of shammy.

Kid and goat skins are chamoised in the same manner as those of sheep, excepting that the hair is taken off without the use of any lime; and that when brought from the mill they undergo a particular preparation called ramalling, the most delicate and difficult of all the others. It consists in this, that as soon as brought from the mill they are steeped in a fit lixivium: taken out, stretched on a round wooden leg, and the hair scraped off with the knife; this makes them smooth, and, in working, cast a fine nap. The difficulty is in scraping them evenly.

SHARK, in ichthyology, the English name of two species of squalus, distinguish

ed by their different colours, blue and white. See SQUALUS.

SHARP (ABRAHAM), in biography, an eminent mathematician, mechanist, and astronomer, was descended from an ancient family at Little Horton, near Bradford, in the west riding of Yorkshire, where he was born about the year 1651. At a proper age he was put apprentice to a merchant at Manchester; but his genius led him so strongly to the study of mathematics, both theoretical and practical, that he soon became uneasy in that situation of life. By the mutual consent, therefore, of his master and himself, though not altogether with that of his father, he quitted the business of a merchant. Upon this he removed to Liverpool, where he gave himself up wholly to the study of mathematics, astronomy, &c. and where for a subsistence he opened a school, and taught writing and accounts,

&c.

He had not been long at Liverpool, when he accidentally fell in company with a meṛchant, or tradesman, visiting that town from London, in whose house it seems the astronomer Flamsteed then lodged. With the view, therefore, of becoming acquainted with this eminent man, Mr. Sharp engaged himself with the merchant as a book-keeper. In consequence he soon contracted an intimate acquaintance and friendship with Mr. Flamsteed, by whose interest and recommendation he obtained a more profitable employment in the dock-yard at Chatham; where he continued till his friend and patron, knowing his great merit in astronomy and mechanics, called him to his assistance in contriving, adapting, and fitting up the astronomical apparatus in the royal observatory at Greenwich, which had been lately built, namely, about the year 1676; Mr. Flamsteed being then thirty years of age, and Mr. Sharp twenty-five.

In this situation he continued to assist Mr. Flamsteed in making observations (with the mural arch, of eighty inches radius, and 140 degrees on the limb, contrived and graduated by Mr. Sharp) on the meridional ze nith distances of the fixed stars, Sun, Moon, and planets, with the time of their transit over the meridian; also the diameter of the Sun and Moon, and their eclipses, with those of Jupiter's satellites, the variation of the compass, &c. He assisted him also in making a catalogue of nearly 3000 fixed stars, as to their longitudes and magnitudes, their right ascensions and polar distances, with