devil; and Paracelsus was thought to have an evil spirit in the pommel of his sword. The language of this prince of alchemists, was a tissue of boasting and falsehood: he promised immortality in this world to his disciples, but his own death, in 1541, opened the eyes of his deluded followers, and blasted their sanguine hopes.

2. The empire of chemistry has been wonderfully extended within the last half century. It is but a short time since this science recognized, as the subjects of her sway, only a few metals and medicines. She has lately subjected to her sceptre, the various kinds of earths found in the composition of our globe--the different fluids with which we are conversant, whether of the aqueous or gaseous form-the various kinds of vegetable, animal, and mineral bodies which surround us--and almost every substance capable of composition or analysis. In short, she has extended her claims to every species of animate and inanimate matter; and maintains authority over a territory of physical science which may be called immense, when compared with her former dominions. B its ancient cultivators, chemistry was chiefly regarded a an object of curiosity, or as a source of amusement; but in the hands of later chemists it has been converted into 2 very instructive, interesting, and invaluable science. The is scarcely an art of human life which it is not fitted to subserve scarcely a department of human inquiry of labour, either for health, pleasure, ornament, or profit, which it may not be made, in its present improved state, eminently to promote.

To the

3. To the husbandman, this science furnishes principles and agents of inestimable value; it teaches him the food of plants-the choice and use of manures-and the best means of promoting the vigour, growth, productiveness, and preservation of the various vegetable tribes. manufacturer, chemistry has lately become equally fruitful of instruction and assistance. In the arts of brewing: tanning, dyeing, and bleaching, its doctrines are precious guides. In making soup, glass, pottery, and all metallic wares, its principles are daily applied; and are capable of still more useful application, as they become better understood. Indeed, every mechanic art, in the different processes of which, heat, moisture, solution, mixture, of

fermentation, is necessary, must ever keep pace, in improvement, with this branch of philosophy. To the physician this science is of still greater value, and is daily growing in importance. He learns from it to compound his medicines, to disarin poisons of their force, to adjust remedies to diseases, and to adopt general means of preserving health.

4. To the student of natural history, the doctrines of chemistry furnish instruction and assistance at every step of his course; as many of his inquiries can be prosecuted with success only through the medium of careful analysis. To the public economist, chemistry presents a treasure of useful information. By means of this science alone, can he expect to attack, with success, the destroying pestilence, so far as it is an object of human prevention; and to guard against other evils to which the state of the elements give rise. And, to the successful prosecution of numberless plans of the philanthropist, some acquaintance with the subject in question seems indispensably necessary. Finally, to the domestic economist, this science abounds with pleasing and wholesome lessons. It enables him to make a proper choice of meats and drinks; it directs him to those measures with respect to aliment, cookery, clothing, and respiration, which have the best tendency to promote health, enjoyment, and cheapness of living. And it puts him on his guard against many unseen evils, to which those, who are ignorant of its laws, are continually exposed. In a word, from a speculative science, chemistry, during the eighteenth century, has become eminently and extensively a practical one,-from an ob scure, humble, and uninteresting place among the objects of study, it has risen to a high and dignified station -and, instead of merely gratifying curiosity, or furnishing amusement-it promises a degree of utility, of which no one can calculate the consequences, or see the end. As it would be quite impossible to give any thing like a representation of the almost interminable field of chemical science, we must content ourselves with a bird's-eye view; and consequently confine our attention to a glance at the following subjects;-atmospheric air, caloric, water, the earths, alkalies, acids, salts, simple combus

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tibles, metals, oxyds, combustion, attraction, repulsion, and affinity.

1. ATMOSPHERIC AIR, contains oxygen, nitrogen, and carbonic acid gas. 1. Oxygen. If the fresh leaves of plants are placed under a glass vessel filled with water, inverted in that fluid, and then exposed to the sun, they emit bubbles of air, which collect at the top of the vessel, and are found to be oxygen gas, or oxygen in an aëriform state. The same kind of air may be obtained by heating nitre in close vessels, or by distilling the black oxyd or calx of manganese with sulphuric acid or oil of vitriol; the gas, however, is most pure when obtained by the latter process. This gas is absorbed by combustible bodies, and converts them into acids. It is essential to the process of combustion whilst burning; and as it unites with bodies that burn, increases their weight, and changes their properties. It is also essential to respiration, no animal being able to live in air which is deprived of oxygen gas. 2. Nitrogen gas, is unfit to maintain combustion or support life; yet a small portion is absorbed in respiration. It is a little lighter than atmospheric air, uninflammable, and one of the most general elements of animal substances. Though nitrogen gas is, by itself, so noxious to animals, it answers an important end when mixed with oxygen gas, in atmospheric air. Were it not for this large quantity of nitrogen in the atmosphere, the blood would flow too rapidly through the vessels, and would shorten the life of man. 3. Carbonic acid gas is incombustible, and does not detonate with oxygen gas. It is noxious to animals.

The atmospheric air which is produced by this mixture, supports animal life by giving out its oxygen and caloric to the blood. The blood in the veins is purple, approaching to black; but when it arrives at the lungs, it imbibes the vital air of the atmosphere, which changes its dark colour to a brilliant red, rendering it the source of internal heat and animal motion. The loss of oxygen, by respira tion and combustion, is supplied by the leaves of trees and other vegetables. They give out during the day a large portion of oxygen gas, which uniting with the nirogen gas thrown off by animal respiration, constantly

preserves the salubrity of the atmosphere. See METEO

ROLOGY.

II. CALORIC. This name is applied to fire, or the substance which produces the sensation we call heat, but never to the sensation itself, or the effect produced by fire. Animal heat is preserved chiefly by the inspiration of atmospheric air. If the hand be put upon a hot body, part of the caloric leaves the hot body and enters the hand; this produces the sensation of heat. On the contrary, if the hand be put upon a cold body, part of the caloric contained in the hand, leaves the hand to unite with the cold body; this produces the sensation of cold. Caloric comes to us from the sun, at the rate of 200,000 miles in a second of time. It may be also procured by combustion, percussion, friction, the mixture of different substances, and by means of electricity and galvanism. absorption of caloric from the atmosphere may be thus seen. If a bottle of wine be removed from the cellar, particularly in summer, it is covered with dew. The bottle being colder than the surrounding air, absorbs caloric from it, and the moisture which that air held in solution, becomes visible, and forms the dew which is deposited on the bottle. Caloric in a latent state, exists in all substances that we are acquainted with, though it combines with different substances in very different proportions.

The

III. LIGHT is considered as a substance consisting of small particles, moving in straight lines, from luminous bodies, with inconceivable rapidity. The effects of light upon vegetation are well known: many flowers follow the course of the sun, and plants that grow in houses make an effort to get at the light. The more plants are exposed to the light, the more colours they acquire. The art of bleaching lettuce, celery, asparagus, &c. is dependent upon the exclusion of light; when exposed to its influence, they turn green. Fine carpets, tapestry, paintings, &c. fade and lose their brilliancy, when exposed to the light. All metallic oxyds become of a deeper colour by being exposed to the sun. Many bodies if exposed to the light combine with it, and emit it again under certain circumstances. These are called solar phosphori. Many animal and vegetable substances also possess this property, as dead

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fish, rotten sea-weeds, the glow-worm, and several other insects.

IV. WATER, is essential to the existence of animals and vegetables. When pure, in which state it is difficultly obtained even by distillation, it is transparent and destitute of colour, taste, or smell. At a temperature below 32 of Fahrenheit it becomes solid and is called ice. When water is heated to the temperature of 212 degrees it boils, and is gradually converted into steam which is an invisible fluid like air, but of less specific gravity. Its elasticity is so great, that it is capable of bursting the vessels in which it is confined, with a violent explosion. Water is composed of oxygen and hydrogen. Hydrogen is the base of the gas which was formerly called inflammable air, and hydrogen gas, from its great levity, has generally been used to fill air balloons. This gas can be procured pure only from water, which in all cases must suffer a decomposition.

V. EARTHS. Notwithstanding the varied appearance of the earth under our feet, and of the mountainous parts of the world, whose diversified strata present to our view substances of every texture and of every shade, the whole is composed of only nine primitive earths; and as three of these occur but seldom, the variety which is produced by the other six becomes the more remarkable. To give a still greater variety to the works of Nature, these earths are endowed with an affinity for acids and metallic oxyds, whence arise the spars, gems, and precious stones of every colour and every species. The nine earths are silica, alumina, zirconia, glucina, yttria, barytes, strontian, lime, and magnesia. Lime is the basis of all mortars and cements, and has an extensive and important use in agriculture; it is employed in all our buildings, and adds much both to the neatness and durability of our dwellings. Silica, is a necessary ingredient in earthen-ware, porcelain, and glass. Barytes is employed in chemical laboratories as a re-agent, and for the formation of salts. Magnesia, being the basis of several salts, is of great use in medicine; and Alumina, by a due mixture with silica, is capable of forming vessels for chemists, that will resist the action of the most concentrated acids. It is the material of which bricks are formed, and is also spread out in strata within