distance between which at one extremity is 0.5 inch, and the other extremity (9.3 inch; and the rules are exactly 24.0 inches in length, and divided into 240 equal parts, called degrees. These degrees commence at the widest end of the scale. The first of them indicates a red heat, or 947° Fahrenheit. The claypieces are small cylinders, baked in a red heat, and made so as to fit 1° of the scale. They are not composed of pure alumina, but of a fine white clay. Alumina is scarcely soluble in water; but may be diffused through that liquid with great facility. Its affinity for water, however, is very considerable. In its usual state it is combined with more than its own weight of water, and we have seen with what obstinacy it retains it. Even this combination of alumina and water is capable, in its usual state of dryness, of absorbing 24 times its weight of water, without suffering any to drop out. It retains this water more obstinately than any of the earths hitherto described. In a freezing sold it contracts more, and parts with more of its water, than any other earth; a circumstance which is of some importance in agriculture. Alumina has no effect upon vegetable blues. It cannot be crystallized artificially; but it is found native in beautiful transparent crystals, exceedingly hard, and having a specific gravity of 4. It is distinguished in this state by the name of sapphyr. It does not combine with metals; but it has a strong affinity for metallic oxydes, especially for those oxydes which contain a maximum of oxygen. Some of these compounds are found native. Thus, the combination of alumina and red oxyde of iron often occurs in the form of a yellow powder, which is employed as a paint, and distinguished by the name of ochre. There is a strong affinity between the fixed alkalies and alumina. When heated together, they combine, and form a loose mass, without any transparency. Liquid fixed alkali dissolves alumina by the assistance of heat, and retains it in solution. The alumina is precipitated again unaltered, by dropping an acid into the solution. This is a method employed by chemists to procure alumina in a state of complete purity; for alumina, unless it be dissolved in alkali, almost always retains a little oxyde of iron and some acid, which disguise its properties. Liquid ammonia is also capable of dissolving a very minute proportion of newly precipitated alumina. Barytes aud strontian also combine with alumina, both when heated with it in a crucible, and when boiled with it in water. The result, in the first case, is

a greenish or bluish-coloured mass, cohering but imperfectly: in the second, two compounds are formed; the first, containing an excess of alumina, remains in the state of an insoluble powder; the other, containing an excess of barytes or strontian, is held in solution by the water. Alumina has a strong affinity for lime, and readily enters with it into fusion. None of the earths is of more importance to mankind than alumina; it forms the basis of china and stone-ware of all kinds, and of the crucibles and pots employed in all those manufactures which require a strong heat. It is absolutely necessary to the dyer and calico-printer, and is employed too with the greatest advantage by the fuller and cleaner of cloth.

ALURNUS, in natural history, a genus of insects of the order Coleoptera. Essen. character: antennæ filiform, short; feelers four to six, very short: jaw horney, arched. There are three species-A. grossus, an inhabitant of South America and India: A. femoratus, found in India: and A. dentipes, found at the Cape of Good Hope.

ALYSSO, or ALYSSUM, mad-wort, in botany, a genus of the Tetradynamia Essculosa class of plants; the flower is of the cruciform kind, and consists of four leaves: the fruit is a small roundish capsule, divided into two cells, in which are contained a num ber of small roundish seeds.

The alyssum is arranged in three divisions, viz. into A. in which the stem is somewhat shrubby: B. stems herbaceous: C. silules inflated, or calyx oblong, closed. There are 33 species; but according to Martyn only 17. All the species may be propagated by seed, and most of them by slips and cuttings. In rich ground they seldom live through the winter in England; but in dry, poor, rubbishy soil, or on old walls, they will abide the cold, and last much longer.

AMALGAM, in the arts. The metals in general unite very readily with one another, and form compounds; thus pewter is a compound of lead and tin, brass is a compound of copper and zinc, &c. These are all called alloys, except when one of the combining metals is mercury; in that case the compound is called an amalgam: thus mercury and gold form a compound called the amalgam of gold.

The amalgam of gold is formed very readily, because there is a very strong affinity between the two metals. If a bit of gold be dipped into mercury, its surface, by combining with mercury, becomes as white as silver. The easiest way of forming this

amalgam is to throw small pieces of red hot gold into mercury heated till it begins to smoke. The proportions of the ingredients are not determinable, because they combine in any proportion. This amalgam is of a silvery whiteness. By squeezing it through leather, the excess of mercury may be separated, and a soft white amalgam obtained, which gradually becomes solid, and consists of about one part of mercury to two of gold. It melts at a moderate temperature; and in a heat below redness the mercury evaporates, and leaves the gold in a state of purity. It is much used in gilding. The amalgam is spread upon the metal which is to be gilt; and then, by the application of a gentle and equal heat, the mercury is driven off, and the gold left adhering to the metallic surface: this surface is then rubbed with a brass wire brush under water, and afterwards burnished. The amalgam of silver is made in the same manner as that of gold, and with equal ease. It forms dentritical crystals, which contain eight parts of mercury and one of silver. It is of a white colour, and is always of a soft consistence. Its specific gravity is greater than the mean of the two metals. Gillert has even remarked, that when thrown into pure mercury, it sinks to the bottom of that liquid. When heated sufficiently, the mercury is volatilized, and the silver remains behind pure. This amalgam is sometimes employed, like that of gold, to cover the surfaces of the inferior metals with a thin coat of silver. The amalgam of tin and mercury is much used in electricity. See GILDING.

AMARANTHUS, in botany, a genus of the Monoecia Pentandria class and order, of the Triandria Trigynia of Gmelin's Linnæus; its characters are, that those species which have male flowers on the same plants with the females have a calyx, which is a five or three-leaved perianthium, upright, coloured, and permanent; the leaflets lanceolate and acute; no corolla; the stamina have five or three capillary filaments, from upright patulous, of the length of the calyx, the anthers ⚫blong and versatile: of those which have female flowers in the same raceme with the males, the calyx is a perianthium the same with the former; no corolla; the pistillum has an ovate germ, styles three, short and subulate; stigmas simple and permanent; the pericarpium is an ovate capsule, somewhat compressed, as is also the calyx on which it is placed, coloured, and of the same size, three-beaked, one-celled, cut open Fransversely; the seed is single, globular,

compressed, and large. There are 22 species, of which we notice A. melancholicus, twocoloured A, with glomerules, axillary, pe. duncled, roundish, and leaves ovate-lanceolate, and coloured. This species varies in the colour of the leaves; being in the open air of a dingy purple on their upper surface, and the younger ones green; in a stove the whole plant is purple-coloured; but it is easily distinguished in all states by its colour, leaves, and the lateness of its flowering after all the others are past: it is joined by La Marck with A, tricolor; a native of Guiana and the East Indies, and cultivated in 1731 by Miller. The obscure purple and bright crimson of the leaves are so blended as to set off each other, and, in the vigorous state of the plants, to make a fine appearance. A. tricolor, three-coloured A: with glomerules sessile, roundish; stem clasping, and leaves lanceolate-ovate, coloured. This has been long cultivated, being in the garden of Gerard in 1596, for the beauty of its variegated leaves, in which the colours are elegantly mixed; these, when the plants are vigorous, are large and closely set from the bottom to the top of the stalks, and the branches form a kind of pyramid, and there. fore there is not a more handsome plant when in full lustre: a native of Guiana, Persia, Ceylon, China, Japan, the Society Isles, &c. A. lividus, livid A. These are the most worthy of a place in the pleasuregarden; but they are tender, and require attention. They are usually disposed in pots, with cocks-combs and other showy plants, for adorning court-yards, and the environs of the house. The seeds of these should be sown in a moderate hot-bed, about the end of March; and when the plants come up, they should have much air in mild weather. When they are fit for transplanting, they should be removed to another moderate hotbed, and placed at six inches distance, watering and shading them till they have taken new root; afterwards they should have free air, and frequent but gentle waterings. In the beginning of June they should be taken up, with large balls of earth to their roots, and planted either in pots or the borders of the pleasure-garden, shaded till they have taken root, and afterwards frequently watered in dry weather. The tree amaranth must be planted in a rich light soil, and if it be allowed room, and well watered in dry weather, it will grow to a large size, and make a fine appearance. The other sorts are sufficiently hardy to bear the open air, and may be sown on a bed of

light earth, in the spring, and when the plants are fit to remove, transplanted into any part of the garden, where they will thrive, and produce plenty of seeds.

AMARILLIS, in botany, a genus of the Hexandria Monogynia class and order, of the natural order of Liliæ or Liliacea; its characters are, that the calyx is a spathe, oblong, obtuse, compressed, emarginate, gaping on the flat side, and withering; the corolla has six petals, lanceolate, the nectary has six very short scales without the base of the filaments; the stamina have six awlshaped filaments, with oblong, incumbent, rising anthers: the pistillum has a roundish, farrowed, inferior germ, the style filiform, almost of the length and in the situation of the stamens, the stigma trifid aud slender; the pericarpium is a subovate, three-celled, three-valved capsule; and the seeds are several. The inflection of the petals, stamens, and pistil is very various in the different species of this genus; and the corolla in most of the species is rather hexapetaloid than six-petalled. Gmelin reckons 27 species. A. lutea, yellow A. or autumnal narcissus, with an undivided obtuse spathe, sessile; flower bell-shaped; corolla erect, shortly tubular at the base, and erect stamens, alternately shorter; the flowers seldom rise above three or four inches high; the green leaves come up at the same time, and when the flowers are past, the leaves increase through the winter. This species recedes a little from the genus. It is a native of the south of France, Spain, Italy, and Thrace; was cultivated by Gerard in 1596, and flowers in September. A. formosissima, jacobea lily, so called, because some imagined that they discovered in it a likeness to the badge of the order of the knights of the order of St. James, in Spain, the lilionarcissus and narcissus of others, with a . spathe undivided, flower pedicelled, corolla two-lipped, nodding, deeply six-parted stamens, and pistil bent down. The flowers are produced from the sides of the bulbs, are large, of a deep red, and make a beautiful appearance: it is a native of America, first known in Europe in 1593, some roots of it having been found on board a ship which had returned from South America, by Simon de Jovar, a physician at Seville, who sent a description of the flowers to Clusius, who published a drawing of it in 1601, called by Parkinson, who figured it in 1629, the Indian daffodil, with a red flower: cultivated in the Oxford Garden in 1653. A. reginæ,

Mexican lily, with spathe, having about two flowers, pedicels divaricating, corollas bellshaped, shortly tubular, nodding, throat of the tube hirsute, and leaves lanceolate, patulous; the bulb is green, corolla scarlet, and at the bottom whitish green, the style red, the flowers large, of a bright copper colour, inclining to red: it flowered in Fairchild's garden, at Hoxton, in 1728; and Dr. Douglas wrote a folio pamphlet upon it, giving it the title of lilium reginæ, because it was in full beauty on the first of March, the queen's birth-day: the roots were brought from Mexico, and therefore Mr. Fairchild called it Mexican lily, the name which it has retained. It flowers in the spring in a very warm stove; is in beauty in February; and in a moderate temperature of air will flower in March or April. A. sarniensis, lilium sarniense of Douglas, who published a description of it in 1725; narcissus of others; Guernsey lily, so called by Mr. Ray in 1665; with petals linear, flat, stamens and pistil straightish, longer than the corolla, stigmas, parted and revolute. The bulb is an oblong spheroid; the leaves are dark willow green; the number of flowers is commonly from eight to twelve, and circumference of each about seven inches; the corolla, in its prime, has the colour of a fine gold tissue, wrought on a rose-coloured ground, and when it begins to fade, it is a pink; in full sunshine, it seems to be studded with diamonds, but by candlelight the specks or spangles appear more like fine gold dust; when the petals begin to wither, they assume a deep crimson colour. The flowers begin to come out at the end of August, and the head is usually three weeks in gradually expanding. This beautiful plant is a native of Japan, and has been long naturalized in Guernsey. It is said to have been brought from Japan to Paris, and cultivated in Morin's garden before 1634. It was cultivated at Wimbledon, in England, by General Lambert, in 1659, and in 1664 became more common: it does not seem to have been in Holland before 1695. The plants are reputed to owe their origin in Guernsey to the shipwreck of a vessel returning from Japan, probably before the middle of the seventeenth century. The bulbs, it is said, being cast on shore, took root in that sandy soil, and produced beautiful flowers, which engaged the attention of Mr. Hatton, the governor's son, who sent roots to several of his friends. A variety of this found at the Cape of Good Hope is des

least. Pitch-coal is sometimes found with amber, and is called black, and is sold to the ignorant at a great price. Specimens inclosing insects, &c. are highly valued, and the amber-dealers are said to be possessed of means of softening it, in order to introduce insects and other foreign bodies into it. Two parts of the empyreumatic oil obtained by distilling mineral pitch boiled several times, with three parts of turpentine, form a compound, which bears a great resemblance to amber, and which is often cut into necklaces and other ornaments, and sold as true amber.

AMBERGRIS, in chemistry, is a substance found floating on the sea, near the coasts of India, Africa, and Brazil, usually in small pieces, but sometimes in masses of 50 or 100 pounds in weight. Various opinions have been entertained concerning its origin. Some affirmed that it was the concrete juice of a tree; others thought it a bitumen; but it is now established, that it is a concretion formed in the stomach or intestines of the physeter macrocephalus, or spermaceti whale. Ambergris, when pure, is a light soft substance which swims on water. Its specific gravity varies from 0.78 to 0.844. Its colour is ash-grey, with brownish yellow and white streaks. It has an agreeable smell, which improves by keeping. Its taste is insipid. When heated to 122° it melts without frothing; if the heat be increased to 212°, it is volatilized completely in a white smoke, leaving only a trace of charcoal. When distilled, we obtain a whitish acid liquid and a light volatile oil; a bulky charcoal remains behind. It is insoluble in water. Acids have little action on it. Weak sulphuric acid occasions no change; but when concentrated, it developes a little charcoal. Nitric acid dissolves it, giving out at the same time nitrous gas, carbonic acid, and azotic gas. A brownish liquid is formed, which leaves, when evaporated to dryness, a brittle brown substance, possessing the properties of a resin. The alkalies dissolve it by the assistance of heat, and form a soap soluble in water. Both the fixed and volatile oils dissolve ambergris. It is soluble also in ether and alcohol. It possesses the properties of the salty matter into which the muscles are converted by nitric acid, and which makes its appearance when dead bodies are allowed to putrefy in great numbers together. This substance has been distinguished by the name of adipocire, from its resemblance both to fat and wax. The quantity of it in

ambergris ataounts to 52.8 parts. Accord ing to the analysis of ambergris made by Bouillon La Grange, it is composed of 52.7 adipocire

30.8 resin

11.1 benzoic acid 5.4 charcoal 100.0

AMBIDEXTER, a person who can use both hands with the same facility, and for the same purposes, that the generality of people do their right hands.

Were it not for education, some think that all mankind would be ambidexters; and, in fact, we frequently find nurses obliged to be at a good deal of pains before they can bring children to forego the use of their left hands. It is to be regretted, that any of the gifts of nature should be thus rendered in a great measure useless, as there are many occasions in life which require the equal use of both hands: such are the operations of bleeding in the left arm, left ancle, &c.

AMBROSIA, in botany, the name of a distinct genus of plants, with flosculous flowers, composed of several small infundibuliform floscules, divided into five segments: these, however, are barren; the fruit, which in some measure resembles a club, growing on other parts of the plant.

This genus belongs to the Monoecia Pentandria class and order. There are five species.

AMBROSINIA, in botany, a genus of the Monoecia Monadelphia class and order; of which there is a species, found in the island of Sicily: spathe one-leafed, sepa. rated by a membranaceous partition, containing the stamina in the hinder cell and upper part of the partition, pistils in the outer cell, and lower part of the partition: the root is tuberous; leaves radical, ovate, and shining.

AMBUSCADE, or AMBUSH, in the military art, properly denotes a place where soldiers may lie concealed, till they find an opportunity to surprise the enemy.

AMELLUS, in botany, a genus of the Syngenesia Superflua: receptacle chaffy: down simple: calyx imbricate: florets of the ray undivided. There are three species.

AMELIORALING crops, in husbandry, are such as are supposed to improve the lands on which they are cultivated. Most of those plants which have a large stem and shady leaf, are thought to render the