magnitude in different vegetables, and exist in the roots, the bark, leaves, and flowers. The trachea, or spiral vessels, which are readily detected in succulent plants, appear in the form of fine threads, and nray be drawn out to a considerable length without breaking. These vessels are very nume rous in all plants, especially under the bark, where they form a kind of ring, and are disposed in distinct bundles, in trees, shrubs, and stalks of herbaceous plants. VEGETABLE acids, in chemistry. The acids which exist in many vegetables are at once recognized by their taste. These acids were formerly denominated essential salts of vegetables, and it was supposed, that all essential salts were the same, and were composed of tartar, or vinegar. But Scheele's discovery of the citric, malic, and gallic acids, which possessing distinct properties from those of tartaric and acetic acids, proved the contrary. Some vegetables contain only one acid, as oranges and lemons, which contain citric acid only. In other vegetables two acids are found, as in gooseberries and currants, the malic, and citric acids; and sometimes three, as the tartaric, citric, and malic acids, which exist together in the pulp of the tamarind. As the acids which exist in vegetables have been already described, under their respective heads, it is now only necessary to enumerate the vegetable acids, specifying at the same time some of the plants from which they are obtained. Acetic acid has been discovered in the sap of some trees, and in the acid juice of eicer arictinum. Oxalic acid exists in combination with potash, in the leaves of the oxalis acetosella, or wood-sorrel. In other species belonging to the same genus, and in some species of rumex, it is in the state of acidulous oxalate of potash. Oxalate of lime has been found in the root of rhubarb. Citric acid is found in the juice of oranges and lemons, in the berries of two species of vaccinium, &c. Malic acid exists unmixed with other acids, in the ap. ple, the barberry, plumb, sloe, elder, &c. In the gooseberry, in the cherry, strawberry, currants, and some other fruits, malic and citric acids are found nearly in equal proportions. Malic acid has been found mixed with tartaric acid in the agave Americana, and in the pulp of tamarinds, along with citric acid. Vauquelin found it combined with lime, forming a malate of lime, in the sempervivum, tectorum or house-leek Gallic acid is found in a great number of plants, and in them it exists chiefly in the bark. Benzoic acid is found in benzoin, balsam of Tolu and Peru, liquid styrax, cinnamon, and vanilla. Fourcroy and Vanquelin suspect that it exists in the anthoxanthum odoratum, or sweet-scented grass, which communicates the aromatic flavour to hay. Prussic acid has been found in the leaves of the lauro-cerasus and peach, in bitter almonds, in the kernels of apricots; and it is supposed that it exists also in the kernels of peaches, of plums, and cherries. It is obtained from the kernels of apricots by distilling water off them with a modét, rate heat; and if lime be added to the concentrated infusion of bitter almonds, a prussiate of lime is formed. Phosphoric acid has been found in different parts of plants; but it is generally combined with lime, forming a phosphate of lime. VEIN, in anatomy, is a vessel which carries the blood from the several parts of the body to the heart. The veins are composed principally of a membranaceous, a vasculous, and a musculous tunic : but these are vastly thinner than in the arteries. See ARTERY. VELEZIA, in botany, so named from Christoval Velezius, examiner, first physician, and demonstrator of botany, in the College of Apothecaries at Madrid, a genus of the Pentrandria Digynia class and order. Natural order of Caryophyllei. Caryophylleæ, Jussieu. Essential character: calyx filiform, five-toothed; corolla five-petalled, small; capsule one-celled; seeds numerous, in a single row. There is but one species viz. V. rigida, a native of the South of Europe. VELLA, in botany, a genus of the Tetradynamia Silicnlosa class and order. Natural order of Siliquosa or Cruciformes. Cruciferæ, Jussien. Essential character: silicle with a partition twice as large as the valves, ovate on the outside. There are two species viz. V. annua, annual vella, or cress rocket; and V. pseudo cytisus, shrubby vella. VELOCITY, swiftness, or that affection of motion whereby a moving body is disposed to run over a certain space in a certain time. In the doctrine of fluxions it is usual to consider the velocity with which magnitudes flow, or are generated. Thus, the velocity with which a line flows, is the same as that of the point, which is supposed to describe or generate the line. The velocity with which a surface flows, is the same as the velocity of a given right line, that, by moving parallel to itself, is supposed to generate a rectangle, always equal to the surface. The velocity with which a solid flows, may be measured by the velocity of a given plain surface that, by moving parallel to itself, is supposed to generate an erect prism, or cylinder, always equal to the solid. The velocity with which an angle flows, is measured by the velocity of a point, supposed to describe the arc of a given circle, which subtends the angle, and measures it. All these velocities are measured at any term of the time of the motion, by the spaces which would be describ. ed in a given time, by these points, lines, or surfaces, with their motions continued uniformly from that term. The velocity with which a quantity flows, at any term of the time, while it is supposed to be generated, is called its fluxion. See FLUXIONS. VELOCITY of bodies moving in curves. According to Galileo's system of the fall of heavy bodies, which is now universally admitted among philosophers, the velocities of a body falling vertically are, at each moment of its fall, as the square roots of the heights from whence it has fallen; reckoning from the beginning of the descent. And hence he inferred, that if a body descend along an inclined plane, the velocities it has, at the different times, will be in the same ratio: for since its velocity is all owing to its fall, and it only falls as much as there is perpendicular height in the inclined plane, the velocity should be still measured by that height, the same as if the fall were vertical. The same principle led him also to conclude, that if a body fall through several contiguous inclined planes, making any angles with each other, much like a stick when broken, the velocity would still be regulated after the same manner, by the vertical heights of the different planes taken together, considering the last velocity as the same that the body would acquire by a fall through the same perpendicular height. This conclusion continued to be acquiesced in, till the year 1672, when it was demonstrated to be false, by James Gre gory, who shows what the real velocity is, which a body acquires by descending down two contiguous inclined planes, forming an obtuse angle, and that it is different from the velocity which a body acquires by descending perpendicularly through the same height; also that the velocity in quitting the first plane, is to that with which it enters the second, and in this latter direction, as ra dius to the co-sine of the angle of inclination between the two planes. This conclusion, however, it is observed does not apply to the motions of descent down any curve lines, because the contiguous parts of curve lines do not form any angle between them, and consequently no part of the velocity is lost by passing from one part of the curve to the other; and bence he infers, that the velocities acquired in descending down a continued curve line, are the same as by falling per pendicularly through the same height. This principle is then applied, by the author, to the motion of pendulums and projectiles. Varignon too, in the year 1693, followed in the same track, showing that the velocity lost in passing from one right lined direc tion to another, becomes indefinitely small in the course of a curve line; and that therefore the doctrine of Galileo holds good for the descent of bodies down a curve line, viz, that the velocity acquired at any point of the curve, is equal to that which would be acquired by a fall through the same perpendicular altitude. VELVET, a rich kind of stuff, all silk, covered on the outside with a close, short, fine, soft shag, the other side being a very strong close tissue. The nap, or shag, called also the velveting, of this stuff, is form. ed of part of the threads of the warp, which the workman puts on a long narrowchanneled ruler or needle, which he after. wards cuts, by drawing`a sharp steel tool along the channel of the needle to the ends of the warp. VENEERING, or VANEERING, a kind of inlaying, whereby several thin slices or leaves of fine woods, of different kinds, are applied and fastened on a ground of some common wood. There are two kinds of inlaying: the one, which is the most common and more ordinary, goes no further than the making of compartments of different woods; the other requires much more art, in representing flowers, birds, and the like figures. The first kind is properly called veneering; the latter is more properly called marquetry. The wood used in veneering is first sawed out into slices or leaves about a line in thickness; i. e. the twelfth part of an inch. In order to saw them, the blocks, or planks, are placed upright, in a kind of sawing press. These slices are afterwards cut into narrow slips, and fashioned divers ways, according to the design proposed; then the joints having been exactly and nicely adjusted, and the pieces brought down to their proper thick ness, with several planes for the purpose, they are glued down on a ground or block, with good strong glue. The pieces being thus jointed and glued, the work, if small, is put in a press; if large, it is laid on a bench covered with a board, and pressed down with poles or pieces of wood, one end of which reaches to the ceiling of the room, and the other bears on the board. When the glue is thoroughly dry, it is taken out of the press and finished; first with lit'tle planes, then with divers scrapers, some of which resemble rasps, which take off the dents, &c. left by the planes. After it has been sufficiently scraped, they polish it with the skin of a sea-dog, wax, and a brush, or polisher of shave-grass; which is the last operation. VENTER, is used in the law for the children by a woman of one marriage. There is a first and second venter, &c. where a man hath children by several wives. VENTILAGO, in botany, a genus of the Pentandria Monogynia class and order. Essential character: calyx tubular; corolla scales protecting the stamens, which are inserted into the calyx; samara winged at the top and one seeded. There is only one species, riz. V. maderaspatana. VENTILATOR, a machine by which the noxious air of any close place, as an hospital, gaol, ship, chamber, &c. may be changed for fresh air. VENTRE inspiciendo, a writ to search a woman that saith she is with child, and thereby withholds lands from the next heir. As if a man, having lands in fee-simple, die, and his widow soon after marry again, and say she is with child by her former husband; in this case, this writ de ventre inspiciendo lies for the heir against her; by which writ the sheriff is commanded, that in presence of twelve men, and as many women, he cause examination to be made, whether the woman is with child or not; and if with child, then about what time it will be born; and that he certify the same to the justices of the assize, or at Westminster, under his seal, and under the seals of two of the men present. Gro. Elizabeth, 506. This writ is now granted, not only to an heir at law, but to a devisee, whether for life, in tail, or in fee. VENTRILOQUISM, an art of speaking, by means of which the human voice and other sounds are rendered audible, as if they proceeded from various different places; though the utterer does not change his place, and in many instances does not appear to speak. It has been supposed to be a natural peculiarity, because few, if any, persons have learned it by being taught; and we have had no rules laid down for ac quiring it. It seems to have been in consequence of this notion that the name ventriloquism has been applied to it, from a supposition that the voice proceeds from the thorax or chest. It has seldom been practised but by persons of the lower classes of society; and as it does not seem to present any advantages beyond that of causing surprize and entertainment, and cannot be exhibited on an extended theatre, the proba bility is that it will continue amongst them. Mr. Gough, in the Manchester Memoirs, and in various parts of Nicholson's Journal, has entertained the opinion that the voice of ventriloquists is made to proceed, in) appearance, from different parts of a room by the management of an echo. But the facts themselves do not support this hypothesis, as a great and sudden variety and change of echoes would be required; and his own judicious remarks, in the same work, on the facility with which we are de ceived as to the direction of sound, are adverse to his theory. From numerous attentive observations, it appears manifest that the art is not peculiar to certain individuals, but may with facility be acquired by any person of accurate observation. It consists merely in an imitation of sounds, as they occur in nature, accompanied with appro priate action of such a description as may best concur in leading the minds of the observers to favour the deception. Any one who shall try, will be a little surprised to find how easy it is to imitate the noise made by a saw, or by a snuffbox when opened or shut, or by a large hand-bell, or a cork cutter's knife, a watch while going, and numberless other inanimate objects; or the voices of animals in their various situations and necessities, such as a cat, a dog, or an hen enraged, intimidated, confined, &c.; or to vary the character of the human voice by shrillness or depth of tone, rapidity or drawling of execution, and distinctness or imperfection of articulating, which may be instantly chang ed by holding the mouth a little more open or more closed than usual, altering the posi tion of the jaw, keeping the tongue in any determinate situation, &c. And every one of the imitations of the ventriloquists will be rendered more perfect by practising them at the very time the sounds are heard, instead of depending on the memory. The leading condition of performance is that the voices and sounds of the dramatic dialogue to be exhibited, should succeed each other so rapidly that the audience should lose sight of the probability that one actor gives effect to the whole, and that where the business is simple the aid of scenery or local circumstance should be called in. We have seen an eminent philosopher of our own time, who had no previous practice of this art, but when speaking on the subject in a mixed company, took up an hat and folding the flaps together said, by way of example, "Suppose I had a small monkey in this hat;" and then cautiously putting his hand in, as if to catch it, he imitated the chatter of the supposed struggling animal, at the same time that his own efforts to secure it had a momentary impression on the spectators, which left no time for them to question whether there was a monkey in it or not: this impression was completed when, the instant afterwards, he pulled out his hand as if hurt, and exclaimed he has bit me." It was not till then that the impression of reality gave way to the diversion arising from the mimic art; and one of the company, even then, cried out "Is there really a monkey in the hat?" ed, and Tom King alone remained to claim the applause. A similar fact may be quoted in the person of that facetious gentleman who has assumed and given celebrity to the name of Peter Pindar. This great poet, laughing at the proverbial poverty of his profession, is sometimes pleased to entertain his friends with unexpected effusions of the art we speak of. One of these is managed by a messenger announcing to the Doctor (in the midst of company) that a person wants to speak with him he accordingly goes out, leaving the door a-jar, and immediately a female voice is heard, which, from the nature of the subject, appears to be that of the Poet's laundress, who complains of her pressing wants, disappointed claims, and of broken promises no longer to be borne with patience. It is more easy to imagine than describe the mixed emotions of the audience. The scene, however, goes on by the Doctor's reply; who remonstrates, promises, and is rather angry at the time and place of this unwelcome visit. His antagonist unfortu nately is neither mollified nor disposed to quit her ground. Passion increases on both sides, and the Doctor forgets himself so far as to threaten the irritated female; she defies him, and this last promise, very unlike the former ones, is followed by payment; a severe slap on the face is heard; the poor woman falls down stairs, with horrid out. cries; the company, of course, rises in alarm; and the Doctor is found in a state of perfect tranquillity, apparently a stranger to the whole transaction. In this manner it was that, at the beginning of the last century, the famous Tom King, who is said to have been the first man who gave public lectures on experimental philosophy in this country, was at tended by the whole fashionable world, for a succession of many nights, to hear him A very able ventriloquist, Fitz James, "kill a calf." This performance was done in a performed in public, in Soho Square, about separated part of the place of exhibition, four years ago. He personated various into which the exhibitor retired alone; and characters by appropriate dresses; and by the imagination of his polite hearers was a command of the muscles of his face he taxed to supply the calf and three butchers, could very much alter his appearance. He besides a dog who sometimes raised his imitated many inanimate noises, and among voice and was checked for his unnecessary others, the repetition of noises of the waterexertions. It appears, from traditional nar- machine at Marli. He conversed with some rative, that the calf was heard to be drag- statues, which replied to him; and also ged in, not without some efforts and con- with some persons supposed to be in the versation on the part of the butchers, and room above, and on the landing place; noisy resistance from the calf; that they gave the watchman's cry, gradually ap conversed on the qualities of the animal, proaching, and when he seemed opposite and the profits to be expected from the the window, Fitz-James opened it and askveal; and that, as they proceeded, all theed what the time was, received the answer, noises of knife and steel, of suspending the creature, and of the last fatal catastrophe, were heard in rapid succession, to the never-failing satisfaction of the attendants; who, upon the rise of the curtain, saw that all these imaginary personages had vanish and during his proceeding with his cry, FitzJames shut the window, immediately upon which the sound became weaker, and at last insensible. In the whole of his performance it was clear that the notions of the audience were governed by the auxiliary |