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vinegur; when purified by distillatiou, it assumes the name of distilled vinegar, usually called acetous acid: when concentrated as much as possible by certain processes, it is called in the shops radical vinegar; but by chemists it is denominated acetic acid, One hundred parts of acetic acid are composed of 50.19 oxygen 13.94 hydrogen 35.87 carbon

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ACETITES, a genus of salts formed by the acetous acid. ACETOUS acid. See Acetic Acid. ACHANIA, in botany, a genus of the Monadelphia Polyandria class, and the natural order of Columniferae. There are three species, viz. the A. malvaviscus, scarlet achania, or bastard hibiscus, which is a native of Mexico and Jamaica; cultivated here in 1714 by the Duchess of Beaufort, and flowering through the greatest part of the year: the mollis, or woolly achania, a native of South America and the West India islands; found in Jamaica by Houstoun, in 1730, and "introduced in 1780 by B. Bewick, Esq. and flowering in August and September: and the pilosa, or hairy achania, a native of Jamaica; introduced in 1780 by Mr. G. Alexander, and flowering in November. Achamia is generally propagated by cuttings, which are planted in pots of light earth, plunged into agentle hot-bed, and kept from the air till they take root, when they should be gradually inured to the open air. They must be preserved in winter in a moderate stove; and kept warm in summer, they will flower, and sometimes ripen fruit. ACHERNER, in astronomy, a star of the first magnitude, in the southern extremity of the constellation Eridanus. See the article ERIDANUs. ACHILLEA, milfoil, in botany, so called from Achilles, who is supposed to have acquired some knowledge of botany from his master Chiron; and to have used this plant for the cure of wounds and ulcers; a genus of the Syngenesia Polygamia Superfina class of plants, and of the natural order of Compositae Discoideae. There are 27 species, of which the most remarkable are the ptarmica, or sneezewort, M. growing wild in all the temperate parts of Europe, found in Britain not uncommonly in meadows, by the sides of ditches, on the balks of corn fields, in moist woods, and shady places. The shoots are put into sallets, and the roots, being hot and biting, are used for the tooth-ache, whence

the plant has been called bastard pellitory, and, on account of the form of the leaf, goose-tongue: the powder of the dried leaves, used as snuff, provokes sneezing, whence the name: in Siberia a decoction of the whole herb is said to be successfully used in internal hemorrhages: of this plant there is a variety with double flowers, called batchelor's buttons; it flowers in July and August, and makes a tolerable appearance: —and the millefolium, common M. or yarrow; abundant in pastures and by the sides of roads, flowering from June to September: mixed instead of hops by the inhabitants of Dalekarlia in their ale, in order to give it an inebriating quality: recommended by Anderson in his Essays on Agriculture, for cultivation, though thought to be a noxious weed in pastures: the bruised herb fresh is recommended by Linnaeus as an excellent vulnerary and styptic, and by foreign physicians in hemorrhages, and thought by Dr. Hill to be excellent in dysenteries, when at!ministered in the form of a strong decoction. An ointment is made of it for the piles, and for the scab in sheep; and an essential oil is extracted from the flowers; but it is not used in the present practice. ACHRAS, or SAPotA-PLUM, in botany, a genus of the Hexandria Monogynia class, and of the natural order of Dumosae. There are four species, viz. The mammosa, or mamme sapota, otherwise called nippled, S. or American marmelade; growing in America to the height of thirty or forty feet,with leaves a foot long, and three inches broad in the middle, cream-coloured flowers, and large oval fruit, containing a thick, luscious pulp, called natural marmelade. This tree is planted for the fruit in Jamaica, Barbadoes, Cuba, and most of the West India islands,

and was cultivated here by Mr. Miller in

1739. Of this there is a variety called the buily, or misberry bully-tree, because it is the tallest of all the trees in the woods: it is esteemed one of the best timber trees in Jamaica. 2. The sapota, which grows to the height of sixty or seventy feet, without knots or branches, and bears a round, yellow fruit, bigger than a quince, which smells well, and is of an agreeable taste. It is common at Panama, and some other places in the Spanish West Indies, but not to be found in many of the English settlements. It was cultivated here by Mr. Miller in 1739. 3. The dissecta, or cloven flowered S. cultivated in Malabar for the fruit, which is of the form and size of an olive, having, pulp of a sweetish acid flavour. Its leaves are used for cataplasms to tumours, bruised and boiled with the root of curcuma and the leaves of ginger; supposed to be a native of the Philippine islands, and probably growing in China, and found by Forster flowering in September, in the island of Tongatabu. 4. The salicifolia, or white willow, S. called in Jamaica the white-bullytree, or galimeta wood, which supplies good timber. The bark of the sapota and mammosa is very astringent, and is called corter jamaicensis. This was once supposed to be the true Jesuits bark, but its effects on the negroes has been permicious. These trees cannot be preserved in England, but with great care and much heat. ACHROMATIC, an epithet expressing a want of colour, introduced into astronomy by De la Lande. AchroMatic telescopes, are telescopes contrived to remedy the aberrations in colours. They were invented by Mr. John Dolland, optician. See Optics, TELE*CoPE. ACHYRANTHES, in botany, a genus of the Pentandria Monogynia class of plants, belonging to the natural order of Miscellanea. There are eleven species, but they have but little beauty, and are only preserved in botanic gardens. ACHYRONIA, in botany, a genus of the Diadelphia Decandria class and order, calyx five-toothed; the lower tooth elongated and cloven: legume compressed, many-seeded; one species, viz. A. villosa, a shrub found in New Holland, with long silky hairs; leaves lanceolate, acute, entire, with silky hair round the margin. ACIA, in botany, a genus of the Monadelphia Dodecandria class and order: calyx five-parted, five petals, drupe dry, coriaceous, fibrous, one-seeded. Two speeies, trees sixty feet high, found in Guiana. ACICARPHA, in botany, a genus of the Poligamia Necessaria class and order: receptacle chaffy, the chaff uniting with the

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tallic oxides and earths, and form with them those compounds called in chemistry salts. Every acid does not possess all these properties, but they all possess a sufficient number to distinguish them from other substances. See C11o M is TRY. ACIDIFIABLE buse, or RAdical, any substance capable of uniting without decomposition with such a quantity of oxygen as to become possessed of acid properties. Almost all the acids agree with each other in containing oxygen, but they differ in their bases, which determine the species of the acid. Sulphur combined with certain portions of oxygen forms sulphurous or sulphuric acid, according to the quantity of oxygen absorbed. ACIDOTON, in botany, a genus of the Monoecia Poliandria class and order; it has male and female flowers on the same, or a different tree. There is but one species, viz. A. urens, a native of Jamaica, which grows to the height of eight or nine feet. ACI PENSER, a genus of fishes of the order Cartilagenei: the characters are, that the head is obtuse, the mouth is under the head, retractile, and without teeth; that the four cerri are below the front, and before the mouth; the aperture of the gills is at the side, the body is elongated and angulated with many series of scuta, or scaly protuberances. These may be ranked among the larger fish; are inhabitants of the sea, but ascend rivers annually; the flesh of all of them is delicious; from the roe is made caviar, and from the sounds and muscular parts is made isinglass; they feed on worms, and other fishes: the females are larger than the males. There are five species: A. sturio, or common sturgeon, inhabits European, Mediterranean, Red, Black, and Caspian seas, and annually ascends rivers in the spring. (See plate I. Ichthyology, fig. 2.) A. schypa, inhabits the Caspian sea, and large lakes of Siberia. A. ruthenus, and A. stellatus, both inhabit the Caspian sea. A. hufo, inhabits the Danube, Wolga, and other Russian rivers, and also the Caspiau. The skin of this species is so hard and tough, as to be used for carriage traces. See STURGEoN. ACNIDA, Virginian hemp, in botany a genus of the Pentandria Pentagynia class and order. There is but a single species, viz. A. cannabina, which is a native of Vir. ginia, and some other parts of America; it is seldom cultivated in Europe. ACONITUM aconite, wolf's-bane, or monk's-hood, in botany, a genus of plants of the Tricynia order and Polyandria class, and pertaining to the natural order of Multisiliquo, in the last edition of Linnaeus, by Gmelin, this genus comprehends fourteen species; most of the species of aconite have been deemed poisonous. The ancients were so surprised at their permicious effects, that they were afraid to touch the plants; and hence sprung many superstitious precautions about the mariner of gathering them. Theophrastus relates that there was a mode of preparing the acouite in his days, so that it should only destroy at the end of one or two years. But some have questioned whether the aconite of Theophrastus, Dioscorides, Pliny, and other ancient writers, be the same with ours, or should be referred to the genus of Ranunculus. It is confidently affirmed, that the huntsmen on the Alps, who hunt the wolves, and other wild animals, dip their arrows into the juice of these plants, which renders the wounds occasioned by them mortal. A decoction of the roots has been used to kill bugs; and the powder disguised in bread, or some other palatable vehicle, has been employed to destroy rats and mice. The A. napellus, or common monk's-hood, has been longness of that portion of its stalk, which is above the spadix, as well as by all its parts, except the florets, being five times smaller than in that plant. It is probably a native of China, and cultivated for the sake of its smell. in pots near the habitations of the Chinese. The sweet flag will succeed very well in moist garden ground, but never produces its spikes, unless it grows in water. The dried roots of the calamus aromaticus are commonly imported from the Levant, though those grown in England are equally good. They have a strong aromatic smell, and a warm pungent taste; the flavour is much improved by drying. The powdered root might perhaps supply the place of foreign spices; and indeed it is the only native aromatic plant of northern climates. It is carminative and stomachic, and often used as an ingredient in bitter infusions. ACOTYLEDONES, in botany, plants so called, because their seeds are not furnished with lobes, and of course put forth no seminal leaves. All mosses are of this kind. See Coty LEDoNEs. ACOUSTICS, in physics, is that science which instructs us in the nature of sound. It is divided by some writers into diacoustics, which explains the properties of those sounds that come distinctly from the somorous body to the ear; and catacoustics, which treats of reflected sounds: but this distinction is not necessary. In the infancy of philosophy, sound was held to be a separate existence; it was conceived to be wafted through the air to our organs of hearing, which it was supposed to affect in a manner resembling that in which our nostrils are affected when they give us the sensation of smell. Yet, even in those early years of science, there were some, and, in particular, the celebrated founder of the Stoic school, who held that sound, that is, the cause of sound, was only the particular motion of external gross matter, propagated to the ear, and there producing that agitation of the organ by which the soul is immediately affected with the sensation of sound. Zeno says, “Hearing is produced by the air which intervenes between the thing sounding and the ear. The air is agitated in a spherical form, and moves off in waves, and falls on the ear, in the same manner as water undulates in circles when a stone has been thrown into it.” The ancients were not remarkable for precision, either of conception or argument, in their discussions, and they were contented with a general and

known as one of the most virulent of all vege

table poisons. Linnaeus says, that it is fatal to swine and goats, but does no injury to horses, who eat it dry. He also informs us, from the Stockholm Acts, that an ignorant surgeon died in consequence of taking the fresh leaves, which he prescribed to a patient. The ef. fluvia of the herb in full flower have produced swooning fits, and a temporary loss of sight. The leaves and shoots of this plant, used as salad, instead of celery, have proved fatal in several instances. But the most powerful part of the plant is the root. Matthiolus relates, that it was given by way of experiment to four condemned criminals, two at Rome in 1524, and two at Prague in 1561, two of whom soon died, and the other two, with great difficulty, were recovered. The juice applied to the wound of a finger, not only produced pain in the arm and hand, but cardialeia, anxiety, sense of suffocation, syncope, &c. and the wounded part sphacelated before it came to suppuration. Dodonaeus says, that five persons at Antwerp died in consequence of eating it by mistake. The effects of this plant are convulsions, giddiness, insanity, violent evacuations, both upwards and downwards, faintings, cold sweat, and even death itself. Nevertheless it has been

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used for medicinal purposes. The Indians are said to use aconite, corrected in cow's urine, with good success against fevers. There is one species of it which has been deemed an antidote to those that are poisonors, called anthora, and those that are poisonous are called thora. The taste of the root of the species denominated anthora, is sweet, with a mixture of bittermess and acrimony, and the smell is pleasant. It purges violently when fresh, but loses its qualities when dricq. This is poisonous as well as the others, though in a slighter degree, and is disused in the present practice. The first person who ventured to introduce the common monk’shood into medicine was Dr. Stoerck. Stoerck recommends two grains of the extract to be rubbed into a powder, witk two drams of sugar, and to begin with ten grains of this powder two or three times a-day. The extract is often given from one grain to ten for a dose; and some have considerably increased the quantity. Instead of the extract, a tincture has been made of the dried leaves, macerated in six times their weight of spirits of wine, and forty drops given for a dose. ACORN, an ornamental piece of wood, in the shape of a cone, fixed to the top of the spindle of a mast-head, above the vane, to keep it from coming off the spindle. ACORUS, in botany, the sweet flag, or sweet rush, a genus of the Monogynia order, and Hexandria class of plants, and belonging to the natural order of Piperita. There are two species, viz. the A. calamus, or common sweet rush, of which there are two varieties, the vulgaris, or European sweet rush, or calamus aromaticus, and the Asiaticus or Indian calamus aromaticus. The common calamus aromaticus grows naturally on the banks of the rivers, and in shallow standing waters; and is found in many parts of England, but is much more plentiful in the standing waters of Holland. and is common in many other parts of Europe. The Indian calamus, which grows not only in marsh ditches, but in more elewated and dry places, in Malabar, Ceylon, Amboyna, and other parts of the East Indies, differs but little from the European, except that it is more tender and narrow, and of a more hot and pungent taste; and A. granuineus, or Chinese sweet-grass, has the roots in tufts, with a few thready fibres. The whole herb has an aromatic smell when

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vague view of things. Some followed the opinion of Zeno, without any farther attempts to give a distinct conception of the explanation, or to compare it with experiment. But in later tissues, during the ardent researches into the phenomena of nature, this became an interesting subject of inquiry. The invention of the air-pump gave the first opportunity of deciding by experiment, whether the elastic undulations of air were the causes of sound; and the trial fully established the point; for a bell rung in vacuo gave uo sound, and one rung in condensed air gave a very loud one. It was therefore received as a doctrine in general physics that air was the vehicle of sound. The celebrated Galileo, the parent of mathematical philosophy, discovered the nature of that connection between the lengths of musical chords and the notes which they produced, which had been ohserved by Pythagoras, or learned by him in his travels in the East, and which he made the foundation of a refined and beautiful science, the theory of music. Galileo shewed, that the real connection subsisted between the tones and the vibrations of these chords, and that their different degrees of acuteness corresponded to the dif. ferent frequency of their vibrations. The very elementary and familiar demonstration which he gave of this connection, did not satisfy the curious mathematicians of that inquisitive age; and the mechanical theory of musical chords was prosecuted to a great degree of refinement. In the course of this investigation, it appeared that the chord vibrated in a manner precisely similar to a pendulum vibrating in a cycloid. It must therefore agitate the air contiguous to it in the same manner: and thus there is a particular kind of agitation that the air can receive and maintain, which is very interesting. Sir Isaac Newton took up this question as worthy of his notice; and endeavoured to ascertain with mathematical precision the mechanism of this particular class of undulations, and gave us the principal theorems concerning the undulations of elastic fluids, which make the 47, &c. Propositions of Book II. of his Principles of Natural Philosophy. They have been considered as giving the doctrines concerning the propagation of sound. Most sounds, we all know, are conveyed to us by means of the air. In whatever manner they either float upon it, or are propelled forward in it, certain it is, that, without the vehicle of this or some other fluid, we should have no sound will be the most distinctly heard.

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The augmentation of sound, by means of

speaking trumpets, is usually illustrated in the following manner: Let ABC, fig. 3, be the tube, BD the axis, and B the mouthpiece for conveying the voice to the tube. Then it is evident when a person speaks at B in the trumpet, the whole force of his voice is spent upon the air contained in the tube, which will be agitated through its whole length, and, by various reflections from the side of the tube to the axis, the air along the middle part of the tube will be greatly condensed, and its momentum proportionably increased, so that when it comes to agitate the air at the orifice of the tube AC, its force will be as much greater than what it would have been without the tube, as the surface of a sphere, whose radius is equal to the length of the tube, is greater than the surface of the segment of such a sphere whose base is the orifice of the tube. For a person speaking at B, without the tubc, will have the force of his voice spent in exciting concentric superficies of air all round the point B; and when those superficies or pulses of air are diffused as far as D every way, it is plain the force of the voice will there be diffused through the whole superficies of a sphere whose radius is BT); but in the trumpet it will be so confined, that at its exit it will be diffused through so much of that spherical surface of air as corresponds to the orifice of the tube. But since the force is given, its intensity will be always inversely as the number of particles it has to move; and therefore in the tube it will be to that without, as the superficies of such a sphere to the area of the large end of the tube nearly. But it is obvious, Dr. M. Young observes, that the confinement of the voice can have little effect in increasing the strength of the sound, as this strength depends on the velocity with which the particles move. Were this reasoning conclusive, the voice should issue through the smallest possible orifice;

cylindrical tubes would be preferable to any

that increased in diameter; and the less the diameter, the greater would be the effect of the instrument; because the plate or mass of air to be moved would, in that case, be less, and consequently the effect of the voice the greater; all which is contradicted by experience. The cause of the increase of sound in these tubes must therefore be derived from some other principles: and among these we shall probably find, that what the ingenious Kircher has sug.

gested is the most deserving of our attention. He tells ns, that “the augmentation of the sound depends on its reflection from the tremulous sides of the tube ; which reflections, conspiring in propagating the pulses in the same direction, must increase its intensity.” Newton also seems to have considered this as the principal cause, in the scholium of Prop. 50, B. II. Princip. when he says, “We hence see why sounds are so much increased in stentorophonic tubes, for every reciprocal motion is, in each return, increased by the generating cause.” Farther, when we speak in the open air, the effect on the tympanum of a distant auditor is produced merely by a single pulse. But when we use a tube, all the pulses propagated from the mouth, except those in the direction of the axis, strike against the sides of the tube, and every point of impulse becoming a new centre, from whence the pulses are propagated in all directions, a pulse will arrive at the ear from each of those points. Thus, by the use of a tube, a greater number of pulses are propagated to the ear, and consequently the sound increased. The confinement too of the voice may have a little effect, though not such as is ascribed to it by some; for the condensed pulses produced by the naked voice freely expand every way; but in tubes, the lateral expansion being diminished, the direct expansion will be increased, and consequently the velocity of the particles, and the intensity of the sound. The substance also of the tube has its effect; for it is found by experiment, that the more elastic the substance of the tube, and consequently the more susceptible if is of these tremulous motions, the stronger is the sound. If the tube be laid on any non-elastic substance, it deadens the sound, because it prevents the vibratory motion of the parts. The sound is increased in speaking-trumpets, if the tube be suspended in the air; because the agitations are then carried on without interruption. These tubes should increase in diameter from the mouth-piece, because the parts vibrating in directions perpendicular to the surface will conspire in impelling forward the particles of air, and consequently, by increasing their velocity, will increase the intensity of the sound : and the surface also increasing, the number of points of impulse and of new propagation will increase proportionally. The several causes, therefore, of the increase of sound in these tubes, Dr. Young concludes to be, 1. The diminution of the lateral, and consequently

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