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a contrary series of phenomena: thus gas, on parting with its heat or atomic motion to otber bodies, becomes liquid, and liquids, by parting with their heat or excited motion, become solids; and the diffusion of heat or atomic motion on such reconversion is sensible, when the oxygenous part of atmospberic air, solidified by respiration, gives out what is called ani. mal heat; and when the same, solidified by combustion, or reduced in volume by compression, gives out heat, and excites the pulsations of light. Phillips's Synopsis,

7. When any body (says SIR H. DAVY) is cooled, it occupies a smaller volume than before ; it is evident, therefore, that its parts must have approached towards each other: when the body is expanded by heat, it is equally evident that its parts must have separated from each other. The immediate cause of the phenomena of heat, then, is motion, and the laws of its communication are precisely the same as all the laws of the communication of motion.

Since all matter also may be made to occupy a smaller volume by cooling, it is evident that the particles of matter must have space between them; and since every body can communicate the power of expansion to a body of a lower temperature, that is, can give an expansive inotion to its particles, it is a probable inference that its own particles are possessed of motion; but, as there is no change in the position of its parts as long as its teroperature is uniform, the motion, if it exist, must be a vibratory or undulatory motion, or a motion of the particles round their axis, or a motion of particles round each other.

It is possible to account for the phenomena of heat, if it be supposed that in solids the particles are in a constant state of vibratory motion, the particles of the hottest bodies moving with the greatest velocity, and through the greatest space; that in fluids, and elastic duids, besides the vibratory motion, which must be conceived greatest in the last, the particles have a motion round their own axis, with different velocities, the particles of elastic fluids moving with the greatest quickness ;

and that, in ethereal substances the particles move round their own axis, and separate from each other, penetrating in right lines through space.

Temperature may therefore be conceived to depend upon the velocities of the vibrations; increase of capacity on the motion being performed in greater space; and the diminution of temperature during the conversion of solids into liquids or gases, may be explained on the principle of the loss of vibra. tory motion, in consequence of the revolution of particles

round their axis, at the moment when the body becomes fluid or æriform, or from the loss of rapidity of vibration in conse. quence of the motion of the particles. Davy's Chemistry.

8. In fine, says Sir R. Phillips, Motions of matter subject to regular mechanical laws, acting absolutely or subordinately, generally or locally, on aggregates or atoms, and producing various densities and different degrees of locomotion and affioity in atoms of matter of different constituent forms, are the proximate causes of all phenomena ; and, as one series of phenomena depends on another, so all existing phenomena are, in regard to others, physically fit, compatible, and harmonious : and, as matter cannot originate its own motion, so, in considering motion as the proximate cause of all phenomena, we arrive, through the ascending series, at the sublime FIRST CAUSE of motion and all phenomena.

518. CARBON is the base of almost all vegetable and animal substances. Charcoal is impure carbon ; and diamond is pure carbon, except a small portion of oxygen with which it has been found to be combined. When combined with oxygen, it forms carbonic oxyde and carbonic acid gas.

Obs.-Carbon exists in large quantities in chalk, lime, stone, &c. From these it is procured in the form of gas, by adding sulphuric acid in a certain apparatus, and sold under the naine of aerated or soda water, which is merely water impregnated with carbonic acid gas. Carbonic acid gas is the choke-damp of mines. Oils, fats, &c. are compounds of Carbon and hydrogen.

519. Oxygen is an element or simple substance diffused generally through nature; and its different combinations are essential to animal life and combustion.

Combined with caloric, it becomes oxygen gas: 100 parts of atmospheric air contain 28 parts of oxygen gas ; and 100 parts water consists of 85 oxygen and 15 nitrogen.

Obs.-Oxygen gas is distinguished from all other gaseous matter by several important properties. Inflammable substances burn in it under the same circumstances as in com. mon air, but with infinitely greater vividness. If a taper, the flame of which has been extinguished, the wick only remaining ignited, be plunged into a bottle filled with it, the dame will be instantly rekindled, and will be very brilliant, and accompanied by a crackling noise. If a steel wire, or

thin file, having a sharp point, armed with a bit of wood in combustion, be introduced into a jar filled with the gas, the steel will take fire, and its combustion will continue to produce a most brilliant phenomenon.

2. Oxygen gas is respirable; a small animal, confined in a jar filled with this gas, lives four or five times as long as in an equal quantity of common alr;-hepce, it has been called vital air.

520. During the burning of any combustible body, the oxygen leaves the atmospheric air, and combines with the calc or residuum, adding to its weight, and forming what is called an oxyde or an acid.

Obs. 1.-This process is called oxygenation ; and if oxy. gen be combined with sulphur, phosphorus, carbon, or any other substance in various degrees, it will produce orydes or acids of strength proportioned to the degree of oxygenation; which are distinguished by the terminations ous and ic ; thus in regard to sulphur and phosphorus, we vary, 1. Oxyde of sulphur; 1. Oxyde of phosphorus ; 2. Sulphurous acid;

2. Phosphorous acid; 3. Sulphuric acid.

3. Phosphoric acid; 2. Combined with metals in various degrees, oxygen pro, duces oxydes of different colours; as grey oxyde of lead, red oxyde of lead, &c.

521. HYDROGEN is one of the most abundant principles in nature; and 15 parts of it combined with 85 of oxygen,

form water. It is only to be met with in the gaseous form; and, being twelve times lighter than atmospheric air, is employed to fill balloons.

It is also inflammable, and is the gas called the fire-damp, so often fatal to miners. It is the chief constituent of oils, fats, spirits, ether, coals, and bitumen.

Obs.-Hydrogen is always produced from water, and WATER is formed by the union of oxygen with HYDROGEN. Its' existence in water is manifested by water in a state of vapour being made to pass over iron wire made red-hot, the oxygen of the water then combines with the iron, the water disappearing, and the hydrogen gas remains.

2. The process for filling balloons, is by mixing five parts of water with one of sulphuric acid; and, by pouring the mix. ture on iron filings, the light gas, by the decomposition of the water, will rise into the balloon; and the balloon, being 12 times lighter than the atmospheric air, will rise through it.

3. Carburetted Hydrogen gas is now very extensively used in lighting the streets of London and other towns. It is distilled from coals, and purified by passing through lime-water, It is then conveyed into a reservoir, called a Gazometer, and from thence through pipes, to light streets, houses, charches, theatres, and shops.

AIR-BALLOON.

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522. NITROGEN, or AZOTE, is a substance generally diffused through nature, and particularly found in animal bodies.

Nitrogen is not to be found in a solid or liquid state; but, when combined with caloric, it forms azotic gas, in which no animal can breathe, or any combustible burn.

Seventy-eight parts combined with 22 parts oxygen, form 100 parts of atmospheric air. In a higher degree of oxygenation, as 30 to seventy, it produces nitrous gas; and still higher, nitric acid.

Obs. 1.--As oxygen is absorbed during burning or breathing, and as soon as the 22 parts, or nearly, of oxygen are absorbed, the remainder is nitrogen, and becomes mephitic, or deadly, being incapable of sustaining life or flame.

2. The reproduction of oxygen appears in the process of vegetation; healthy plants exposed in the sunshine to air, containing small quantities of carbonic acid gas, destroy that elastic fluid and evolve oxygen gas; so that the two classes of organized beings are thus dependant.

3. It has lately been found, that azote generates uric acid, and gravel in the stones and kidneys, and hence animal food has properly been forbidden to persons subject to those afflicting disorders.

523. Chlorine, or oxymuriatic Acid Gas, is an elementary substance, of a yellowish green colour, and it is this circumstance which suggested its name. Its odour is extremely disagreeable. It is not capable of being respired. And even when mixed in very small quantities with common air, renders the air extremely pernicious to the lungs. When an inflamed taper is introduced into a phial filled with it, the light continues, but of a dull red colour.

Obs.-Chlorine has never been found pure in nature, but exists in many compounds, particularly in common salt, and it may even be produced from that substance.

524. SULPHUR is an inflammable substance found in the neighborhood of volcanoes, combined with earths and metals, from which it is separated by sublimation in a furnace.

Obs.-When combined with oxygen, it forms a sulphuric and sulphurous acid. This is usually done by burning the Bulphur in leaden chambers, the floors of which are covered with water, with a quantity of nitre (that is, one part to nine parts of sulphur) which affords oxygen for the formation of the acid which is condensed by the water. The water is then drawn off, evaporated by boiling, and afterwards distilled in retorts: the result is sulphuric acid, or oil of vitriol. Sulphur combines with hydrogen, the alkalies, the earths, and metals. These combinations are called sulphurets.

525. Phosphorus is a simple substance, found in a state of combination with the bones of animals, from which it is extracted.

Its tendency to unite with oxygen is so great, that it always burns in the open air; and bursts into flame, at a degree of heat a little above that of the human body.

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