evolved, than when combustion takes place in the atmosphere. HYDROGEN is also a permanently elastic fluid. It is the lightest body with which we are acquainted, and is employed, in combination with other gases, to inflate balloons. A bladder filled with this gas will ascend in the atmosphere in the same manner as a piece of cork plunged, to the bottom, will rise in

water.

CHLORINE is a gaseous body of a yellowish green color, a strong, suffocating smell, and a very astringent taste. If breathed undiluted, it destroys animal life; yet it not only supports combustion, but possesses the remarkable quality of setting fire to many of the metals, even at the common temperature of the air, when they are beaten out into thin leaves and introduced into it. The combinations of metals with chlorine are called chlorides. Chlorine possesses the property of destroying all vegetable colors, and of rendering vegetable bodies exposed to its action white. This property renders it useful in bleaching: combined with hydrogen, it forms muriatic acid, which, united with oxides, produces an immense number of salts, such as common sea-salt, which is a muriate of soda.

CARBON, or charcoal, is found in many different forms, and can be prepared by burning wood, &c., in close vessels. The diamond is pure carbon; and plumbago, or black lead, is principally composed of this substance united with a little iron. It combines with all the supporters of combustion, and, with oxygen, forms carbonic acid. SULPHUR, or brimstone, we shall describe hereafter in the chapter upon minerals. When heated to 170 degrees, it becomes volatilized, and the

result is a fine powder denominated flowers of sulphur. Combined with oxygen, it forms sulphuric acid, or oil of vitriol.

PHOSPHORUS is chiefly prepared from bones, which consist mostly of the phosphate of lime. It is an amber-colored and semi-transparent solid, so very combustible that it takes fire in the air, emitting a white smoke having a smell of garlic. It also appears luminous in the dark.

Such is a brief description of some of the most important of the simple or elementary bodies which compose all known substances. Others we shall hereafter notice in the article on minerals. In a general summary, we may state that the simple bodies, or those which have never been decomposed, are fifty-four in number; and, for the convenience of study, they have been divided into metallic and non-metallic substances. The non-metallic elements are again divided into gazolytes, or bodies which are permanently gaseous; metalloids, or bodies which resemble the metals in their chemical relations; and halogens, or bodies which produce salts when in union with the metals. The nonmetallic elements are thirteen in number,—namely, oxygen, hydrogen, nitrogen, chlorine, iodine, bromine, fluorine, boron, carbon, silicon, sulphur, selenium, and phosphorus. The first three are the gazolytes, the next four the halogens, and the remaining six the metalloids. The metallic elements are forty-one in number, namely, potassium, sodium, lithium, calcium, borium, strontium, magnesium, aluminum, thorium, glucium, zirconium, yttrium, manganese, zinc, iron, tin, cadmium, cobalt, nickel, arsenic, chromium, vana

dium, molybdenum, tungsten, columbium, antimony, uranium, cerium, bismuth, titanium, tellurium, copper, lead, mercury, silver, gold, platina, palladium, rhodium, osmium, and iridium. These metallic elements are again divided into three orders, the first twelve being the bases of the alkalies and earths; the next twentyone being metals whose oxides are not reduced by heat alone, and the remaining eight, whose oxides are reduced by a red heat.

From these fifty-four elementary substances are formed all the beautiful varieties of terrestrial objects: nor is there any thing very wonderful or mysterious in this fact; since, as we have seen, any given two of them, if made to unite in different proportions, are capable of producing the most opposite substances. Thus nitrogen and hydrogen, combined in certain proportions, form the vital air which we breathe; the same elements, combined in another proportion, produce an intoxicating gas; and again, in still another, produce aquafortis, which is a deadly poison. It is also to be observed that new substances, thus produced, united with each other, give rise to new compounds, which are susceptible of being combined, and so on through an almost infinite diversity of chemical union. From recent experiments in chemistry, however, it has been suggested that all substances whatever are but modifications of one primitive element; but the absolute truth of this startling theory remains to be practically demonstrated.

THIS science proposes to investigate the natural history of the earth- especially the general structure of what may be called its crust, or shell. It does not entirely overlook the internal strata, or even the nucleus, of our globe; but as these are beyond our inspection, it is possible to offer little more than speculations respecting them.

This noble science is of modern date. Certain theories had, indeed, been offered upon this subject;

but the extravagance of these, proceeding, as they often did, from men of the highest talent, affords humiliating lessons as to the absurdities in which the master-spirits of our race may be involved, when their footsteps do not follow the paths of experiment and observation. The great mathematician Kepler attempted to prove that the earth was a vast animal; the tides he regarded as occasioned by the heavings of its prodigious lungs. Lato and the Stoics seem to have entertained a similar opinion. Whiston, the English divine, considered the earth as produced by the condensation of a comet, and the deluge as occasioned by the visit of one of those erratic orbs.

Other theorists have ascribed the origin of the globe to fragments which have fallen successively from the heavens, in the form of aërolites. Our own Captain Symmes, of Cincinnati, seriously maintained that the earth was hollow, and inhabited, and that the interior was accessible by openings at the poles. He brought a vast deal of learning to the support of his theory, and even undertook to equip an expedition for the purpose of exploring the polar regions, in order to determine the question by observation. Perhaps, however, the palm of absurdity must be awarded to Voltaire, who accounted for the immense masses of sea-shells, found upon the mountains of Geneva, by supposing them to have been thrown there from the wallets of pilgrims in the holy wars! Such are some of the follies into which the highest intellect may be led, either by a partial observation of facts, or the adoption of a false philosophy.

The application of Lord Bacon's rule, which instructs