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ral. The hints suggested will be sufficient to evince its general and particular importance, and induce some, perhaps, to follow up with care and correctness, a practice which alone can enable them to give the fair results of interesting experiments, or qualify them to ascertain the particular causes of success or failure in general management. The obscurity and perplexity of conjecture can by such means alone be changed, for the clearness of fact and the beauty of order; and, in short, they can thus only decide with truth, and act with confidence. AGRIMONIA, agrimony, in botany, a genus of Dodecandria Digynia class and order: the calyx is one-leafed, permanent, perianthium fenced with an outer calyx; the corolla has five petals; the stamina are capillary filaments, shorter than the corolla; the anthers are small; the pistillum is a germ inferior; the style simple; the stigmas obtuse; no pericardium; there are two roundish seeds. Of this genus there are five species: the A. parviflora grows in the borders of corn-fields, shady places, and hedges in Great Britain, and most parts of Europe; it is perennial, and flowers in June and July. The root is sweet-scented; an infusion of it is used by the Canadians with success in burning fevers. Dr. Hill says, that an infusion of six ounces of the crown of the root in a quart of boiling water, sweetened with honey, and drank to the quantity of half a pint, thrice a day, is a cure for the jaundice. When the plant comes into flower, it will dye wool of a bright full nankeen colour; if gathered in September, it yields a darker yellow. In Prussia it is used for dressing of leather. AGROSTEMA, the garland of the field, in botany, a genus of the Decandria Pentagynia class and order: the calyx is oneleafed; the corolla has five petals; the stamina are ten awl-shaped filaments; the pistillum an ovate germ, with erect styles and simple stygmas; the pericarpium is onecelled; the seeds are numerous. There are four species, viz. 1. A. githago, corns campion, or cockle: 2. A. coronaria, rosecampion: 3. A. flos jovis: and 4. A coeli rosa, smooth campion. The first species is a common annual weed in corn fields, and flowers in June or July; the seeds are black, with a surface like shagreen, and appear in the microscope like a hedge-hog rolled up. The second species is biennial, a native of Italy, the Valais, and Siberia; but so long an inhabitant of English gardens, that it is become a kind of weed. Of

this plant there are three varieties, one with deep red, another with flesh-coloured, and a third with white flowers; but they are not much esteemed, as the double rose-campion, which is a fine flower, has excluded the others from most good gardens. The single rose-campions are sufficiently propagated by the self-sown seeds. The variety with double flowers, having no seeds, is propagated by parting the roots in autumn, and planting them in a border of fresh undunged earth, at the distance of about six inches; they should be watered gently till they have taken root; afterwards wet, as well as dung, is injurious to them. In spring they should be removed into the borders of the flower-garden, where they will be very ornamental whilst they flower in July and August. The third species grows naturally on the Swiss and Piedmontese mountains, and in the Palatinate, and was cultivated in 1739, by Mr. Miller. It flowers in July, and the seeds ripen in September. It will thrive best in a moist soil, and a shady situation. The fourth species is annual. It is a native of Italy, Sicily, and the Levant, but being a plant of little beauty, it is preserved in botanic gardens merely for variety. AGROSTIS, bent-grass, in botany, a genus of the Triandria Digynia class of plants, the calyx of which is composed of a glume, consisting of two valves, and inclosing a single flower; it is of an acuminated figure; the corolla is also of an acuminated figure, and composed of two valves; it is scarce so long as the cup, and one of the valves is larger than the other, and aristated; the corolla serves in place of a pericarpium; it surrounds and every way incloses the seed, which is single, roundish, and pointed at each end. There are 42 species, distributed into two classes; the aristatae, or those with awns; and the mutica", or naked without awns. The A. spica venti, silky bent grass,

with entire petals, the outer one having a

stiff, straight, and very long awn, and the panicle spreading; is an annual, and common in sandy corn-fields. It flowers in June and July, and is liable to be smutted. Horses and goats eat it, but sheep refuse it. The A. arundicea, furnished with a writhed awn; is a native of many parts of Europe, and is a perennial. The Kalmuc Tartars weave mats of it, and thatch their houses with it. The alba, or white bentgrass, is perennial, and grows in ditches, marshes, and moist meadows : there are four varieties, some of which are found among potatoes in light sandy soils, and some among wheat, flowering from July to September, Agüe. See MEDICINE. AGYNEIA, in botany, a genus of the Triandria Monogynia class and order: the male flowers are below the female, the calyx is six-leaved; no corolla; in the male, instead of filaments, are three or four anthers: in the female flowers, the germ of the size of the calyx; neither style nor stigma. There are two species, viz. A. impubes, with leaves smooth on both sides; and A. pubera, with leaves downy underneath: both species are natives of China. AID de-camp, in military affairs, an officer employed to receive and carry the orders of a general. He ought to be alert in comprehending, and punctual and distinct in delivering them. He is seldom under the degree of a captain, and all aids-de-camp have ten shillings a day allowed for their duty. AIGUISCE, AIGUIsse, EGUisce, in heraldry, denotes a cross with its four ends sharpened, but so as to terminate in obtuse angles. It differs from the cross fitchée, in as much as the latter goes tapering by degrees to a point, and the former only at the ends. AILANTHUS, in botany, a genus of plants of the Decandria Trigynia class and order: it has male, female, and hermaphrodite flowers. The calyx of the male is one-leafed; the torolla has five petals; the stamina have ten filaments, the anthers are oblong and versatile. The calyx and corolla of the female are the same as those of the male; the pistillum has from three to five germs; the styles are lateral, and the stigmas capitate ; the pericardium has as many capsules as there are germs; the seeds are solitary. The calyx and corolla of the hermaphrodite is the same with those of the male and female; the stamina have two or three filaments; the pistillum, pericarpium, and seed as in the female. There is one species, viz. A. glandulosa, or tall ailanthus, which is a tree with a sraight trunk, 40 or 50 feet high, a native of China. It grows fast in our climate, and as it rises to a considerable height it is proper for ornamental plantations. A resinous juice, which soon hardens, flows from the wounded bark. The wood is hard, heavy, glossy like satin, and susceptible of a fine polish. AILE, or AIEL, in law, a writ which lies where a person's grandfather, or great grandfather, being seised of lands, &c. in feesimple the day that he died, and a stranger

abates or enters the same day, and dispossesses the heir of his inheritance. AJOVEA, in botany, a genus of the Hexandria Monogynia class and order: the calyx is single-leaved, the corolla has three petals, the stigma is divided into six segments, and the fruit is a roundish, singlecelled, monospermous berry. There is one species that grows in the forests of Guiana. AIR, a thin elastic fluid, surrounding the globe of the earth. It is compounded principally of two gases, viz. oxygen and azote, together with a variety of other substances, suspended or dissolved therein. The mechanical and chemical effects of this extensive fluid mass are discussed under various heads of science. See ATMosphere, CHEMistry, and the articles thence referred to. AiR, in music, generally speaking, is any melody, the passages of which are so constructed as to lie within the province of vocal expression, or which, when sung or played, forms that connected chain of sounds which we call tune. The strict import of the word is confined to vocal music, and signifies a composition written for a single voice, and applied to words. AIR-gun, a machine for exploding balls by means of condensed air. Authors describe two kinds of this machine, viz, the common one, and what is called the magazine air-gun. See PNEUMAtics. AIR-pipes, a contrivance invented by Mr. Sutton, a brewer of London, for clearing the holds of ships, and other close places, of their foul air. The principle upon which this contrivance is founded is well known. It is no other than the rarefying power of heat, which, by causing a diminution of the density of the air in one place, allows that which is in contact with it to rush im, and to be succeeded by a constant supply from remoter parts, till the air becomes every where equally elastic. If a tube, then, be laid in the well-hold, or any other part of . a ship, and the upper part of this tube be sufficiently heated to rarefy the impending column of air, the equilibrium will be maintained by the putrid air from the bottom of the tube, which being thus drawn out, will be succeeded by a supply of fresh air from the other parts of the ship; and by continuing the operation, the air will be changed in all parts of the ship. Upon this principle, Mr. Sutton proposed to purify the bad air of a ship, by means of the fire used for the coppers, or boiling places, with which every ship is provided. Under every suck

copper or boiler, there are two holes separated by a grate, one for the fire and the other for the ashes; and there is also a slue, communicating with the fire-place, for the discharge of the smoke. The fire, after it is lighted, is preserved by the constant. draught of air through these two holes and the flue; and if the two holes are closed, the fire is extinguished. But when these are closed, if another hole, communicating with any other airy place, and also with the fire, be opened, the fire will of course continue to burn. In order to clear the holds of the ships of the bad air, Mr. Sutton proposed to close the two holes above mentioned, viz. the fire-place and ash-place, with substantial iron doors, and to lay a copper or leaden pipe, of sufficient size, from the hold into the ash-place, and thus to supply a draught of air for feeding the fire; a constant discharge of air from the hold will be thus obtained, and fresh air will be supplied down the hatches, and by such other communications as are open into the hold. If other pipes are connected with this principal pipe, communicating either with the wells or lower decks, the air that serves to feed the fire will be drawn from such places. Air-shafts, among miners, are holes made from the open air to meet the adits, and supply them with fresh air. These, when the adits are long, or exceeding thirty or forty fathoms, become highly necessary, as well to give vent to the damps and noxious vapours, as to let in fresh air. AIR-trunk, a simple contrivance by Dr. Hales, for preventing the stagnation of putrid effluvia, and purifying the air in jails and close rooms; which consists of a square trunk open at both ends, one of which is fixed in the ceiling, and the other is extended to a considerable height above the roof. The noxious effluvia, ascending to the top of the room, escape by this trunk. Some of these have been mine, and others six inches in the clear; but whatever be their diameter, their length should be proportionable, in order to promote the ascent of the vapour. As the pressure of fluids, and consequently of the air, corresponds to their perpendicular altitude, the longer these trunks are, so much the greater will be the difference between columns of air pressing at the bottom and at the top; and of course so much the greater will be their effect. See VENTILATor. AiR-vessel, in hydraulics, is a name given to those metalline cylinders, which are placed between the two forcing-pumps in

the improved fire-engines. The water is injected by the action of the pistons through two pipes, with valves, into this vessel; the air previously contained in it will be compressed by the water, in proportion to the quantity admitted, and by its spring force the water into a pipe, which will discharge a constant and equal stream; whereas in the common squirting engine the stream is discontinued between the several strokes. Other water-engines are furnished with vessels of this kind. AIR-ressels, in botany, are certain camals, or ducts, whereby a kind of absorp. tion and respiration is effected in vegetable bodies. Air-vessels have been distinguished from sap-vessels; the former being supposed to correspond to the trachea and lungs of amimals; the latter to their lacteals and bloodvessels. Dr. Grew, in an inquiry into the motion and cause of the air in vegetables, shews, that it enters them various ways, not only by the trunk, leaves, and other parts above ground, but at the root. For the reception, as well as expulsion of the air, the pores are so very large in the trunks of some plants, as in the better sort of thick walking-canes, that they are visible to a good eye without a glass; but with a glass the cane seems as if it were stuck full of large pin-holes, resembling the pores of the skin in the ends of the fingers and ball of the hand. In the leaves of the pine, through a glass, they make an elegant shew, standing almost exactly in rank and file throughout the length of the leaves. But though the air enters in partly at the trunk, and also at other parts, especially in some plants, yet its chief admission is at the root: much as in animals, some part of the air may continually pass into the body and blood by the pores of the skin; but the chief draught is at the mouth. If the chief entrance of the air were at the trunk, before it could be mixed with the sap in the root it must descend; and so move not only contrary to its own nature, but in a contrary course to the sap : whereas, by its reception at the root, and its transition from thence, it has a more natural and easy motion of ascent. The same fact is farther deduced from the finemess and smallness of the diametral apertures in the trunk, in comparison of those in the root, which nature has plainly designed for the separation of the air from the sap, after they are both together received into them. Air-vessels are found in the leaves of all plants, and are even discoverable in many without the help of glasses; for upon breaking the stalk or chief fibres of a leaf, the likeness of a fine woolly substance, or rather of curious small cobwebs, may be seen to hang at both the broken ends. This is taken notice of not only in some few plants, as in scabious, where it is more visible; but may also be seen more or less in most others, if the leaves be very tenderly broken. This wool is really a skein of air-vessels, or rather of the fibres of the air-vessels, loosed from their spiral position, and so drawn out in length. AIRA, hair-grass, in botany, a genus of the Triandria Digynia class and order, and of the natural order of Grasses. There are twenty-five species, some of which have awns and others have none. The A. aquatica, water hair-grass, generally grows in the margin of pools and watery places, running into the water to a considerable distance, and is known by the purple or bluish colour of the panicles, and sweet taste of the flowers. It is a perennial, and flowers in May and June. To this grass has been attributed the sweetness of Cottenham cheese, and the fineness of Cambridge butter. The A. caespitosa, or turfy-hair grass, grows in moist meadows and woods, is perennial, it flowers in June and July, sometimes trailing on the ground to the length of several fect, and the panicle exhibiting a beautiful silky appearance: cows, goats, and swine eat it, but horses are not fond of it. It is the roughest and coarsest grass that grows in pastures or meadows, and is called by the common people hassocks, rough-caps, and bull's faces. To get rid of it, the land should be first drained, and the tufts of the noxious weeds pared off and burnt. The ashes yield a good manure. The A. flexuosa, or waved mountain grass, is the principal grass on Banstead Downs, and the Mendip Hills. It is difficult of cultivation. AITONIA, in botany, so called from Mr. Aiton, his Majesty's late gardener at Kew, a genus of the Monadelphia Octandria class and order, and of the natural order of Columniferae. There is but one species, viz. A. capensis, found at the Cape of Thunberg. It has a shrubby stalk six feet high, and a fruit resembling that of the winter cherry. With us it is of slow growth, and seldom exceeds three feet in height. At a sufficient age it produces flowers and fruit through the greatest part of the year. AJUGA, bugle, in botany, a genus of the Didynamia Gymnospermia class of plants: he flower is monopetalous and ringent; the

upper lip being small and bifid; the lower one’ large and trifid: there is no pericarpium: the seeds are contained in the cup of the flower, and are four in number. There are 10 species. AIZOON, in botany, a genus of the Polyandria Pentagynia: the calyx is a oneleafed perianthium; no corolla; the stamina have many capillary filaments; the anthers are simple, the pistillum has a five-cornered germ, the seeds are several: there are ten species, all belonging to the hot climates. ALA, in botany, is used in differentsenses; sometimes it denotes the hollow between the stalk of a plant and the leaves; sometimes it is applied to the two side petals of the papilionaceous flowers, the upper petal being called the vexillum, and the lower one the carina; others use it for the slender membranaceous parts of some seeds, thence said to be alated; and others, again, for the membranaceous expansions found on the stems of plants, thence denominated alated stalks. ALABASTER, a well known description of stone used by statuaries and others. It is the sulphate of lime. See Chemistry and MiNERALogy. ALHE, in anatomy, is sometimes used for the lobes of the liver, the nymphae of the female pudendum, the two cartilages which form the nostril, the arm-pits, young stems or branches, &c. ALANGIUM, in botany, a genus of the Decandria Monogyria class and order; the characters of which are, that it has from 6 to 10 linear petals, from 10 to 12 stamina; the calyx dentated; the fruit a spherical berry, single-celled, containing from one to three seeds: there is only one species, viz, A. pungens. ALATED in botany, an epithet applied to the seed, stem, or leaf-stalk; a seed is alated, when it has an ala or membrane af. fixed to it, which, by its flying, serves to disperse it. The foot stalk of a leaf is alated, when it spreads out the sides. Alated leaves are those made up of several pinnated ones. ALAUDA, lark, in ornithology, a genus of birds of the order of Passeres; the characters of which are, that the beak is cylindrical, subulate, and straight, bending towards the point, the mandibles are of equal size and opening downwards at their base; the tongue is bifid; and the hinder claw is straighter and longer than the toe. Pennant adds, that the nostrils are covered with feathers or bristles, and the toes divided to their origin. There are 33 species, but we shall notice only two of them. 1. A. arvensis, or sky-lark, the specific characters of which are, that the two outermost quills of its tail are white lengthwise externally, and the intermediate ones are ferruginous on the inside: the length is about seven inches. The males of this species are somewhat browner than the females; they have a black collar, and more white on the tail; their size is larger, aud their aspect bolder; and they exclusively possess the faculty of singing. When the female is impregnated, she forms her nest between two clods of earth, and lines it with herbs and dry roots, being no less attentive to the concealment than to the structure of it. It sometimes builds its nest among corn and in high grass. Each female lays four or five eggs, which are greyish, with brown spots; and the period of her incubation is about 15 days. The young may be taken out of the nest when they are a fortnight old, and they are so hardy, that they may be easily brought up. The parentis very tender of her young; and though she does not always cover them with her wings, she directs their motions, supplies their wants, and guards them from danger. The common food of the young sky-larks is worms, caterpillars, ants-eggs, and even grasshoppers; and in maturity, they live chiefly on seeds, herbage, and all vegetable substances. Those birds, it is said, that are destined for singing, should be caught in October or November; the males should, as much as possible, be selected: and when they are untractable they should be pinioned, lest they injure themselves by their violence against the roof of the cage. As they cannot cling by the toes, it is needless to place bars across their cage; but they should have clean sand at the bottom of it, that they may welter in it and be relieved from the vermin which torment them. In Flanders, the young ones are fed with moistened poppyseeds and soaked crumbs of bread; and when they begin to sing, with sheep's and calves' hearts, hashed with hard eggs; to which are added, wheat, spilt-oats, millet, linseed, and the seeds of poppy and hemp, steeped in milk. Their capacity of learning to sing is well known; and so apt are some cock larks, that, after hearing a tune whistled with the pipe, they have caught the whole, and repeat it more agreeably than any limnet or canary bird. In summer the larks seek the highest and driest situations; but in winter they descend to the plains, and assemble in numerous flocks. In the former season they are very lean, and in the latter very fat, as they are always on the ground, and constantly feeding. In mount

ing the air, they ascend almost perpendicularly, by successive springs, and hover at a great height; but in descending, they make an oblique sweep, unless they are pursued by a ravenous bird, or attracted by a mate, in either of which cases they fall like a stone

These small birds, at the height to which they soar, are liable to be wafted by the wind; and they have been observed at sea, clinging to the masts and cordage of ships. Sir Hans Sloane observed some of them 40. miles from the coast, and Count Marsiglimet with them on the Mediterranean. It is conjectured, that those which are found in America have been driven thither by the wind. Some have supposed, that they are birds of passage, at least in the more southern and milder climates of Europe; but they are occasionally concealed under solue rock or sheltered cave. The lark is found in all the inhabited parts of both continents, as far as the Cape of Good Hope; this bird, and the wood-lark, are the only birds which sing whilst they fly. The higher it soars, the more it strains its voice, and lowers it till it quite dies away in descending. When it ascends beyond our sight, its music is distinctly heard; and its song, which is full of swells and falls, and thus delightful for its variety, commences before the earliest dawn. In a state of freedom, the lark begins its song early in the spring, which is its season of love and pairing, and continues to warble during the whole of the summer. The Honorable Daines Barrington reckons this among the best of the singing larks: and as it copies the warble of every other bird, he terms it a mocking-bird. These birds, which are esteemed a delicacy for the table, though Linnaeus thinks the food improper for gravelly complaints, are taken with us in the greatest numbers, in the neighbourhood of Dunstable. The season begins about the 14th of September, and ends the 25th of February; and during this time, about 4000 dozen are caught for sup: plying the London markets. Those caught in the day, are taken in clap-nets, till the 14th of November. But when the weather becomes gloomy, and also in the night, the larker makes use of a trammel-met, 27 or 28 feet long, and five broad, which is put on two poles 18 feet long, and carried by men under each arm, who pass over the fields, and quarter the grounds as a setting dog. When they see or feel a lark strike the net, they drop it down, and thus the birds are taken. The darkest nights are the most proper for their sport; and the met will not only take larks, but all other birds that roost

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