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HITHERTO we have considered the action of bodies on each other in masses, or what is called their mechanical actions; and for this purpose it was not necessary to attend particularly to the difference in the many species or kinds of matter, which we distinguish more or less readily.

But if we present bodies of different kinds to each other in proper circumstanccs, a certain action takes place between the minute particles of one sort of substance upon those of another sort, by which, frequently, the individual or peculiar properties of each disappear, and a new substance is formed.

The study of this action of the minute or ultimate particles of different kinds of matter on each other is called chemistry, and the powers thus exerted occasion chemical actions.

Independently of the enlargement of our views of nature, and the pleasure and entertainment derived from contemplating her operations, chemistry is essentially useful in many of the arts upon

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which the comforts, and even the very existence, of civilized life, depend.

As examples, we may mention the arts of dyeing, bleaching, tanning, potting, glass-making, baking, brewing, distilling, working metals, &c. &c. which owe their present state of perfection to the science of chemistry In agriculture it is capable of affording great assistance, by explaining the nature of soils and manures; and in medicine its importance is invaluable, many of the most efficacious remedies being entirely formed by chemical

processes. In short, there is scarcely any art or trade which either does not altogether depend upon, or may be benefited by this science.

By chemical means we are enabled to reduce compound bodies to the constituent principles of which they are composed, and this operation is called analysis, or decomposition. When a substance cannot by any means be resolved into others, it is called a simple body; and it is now known that all that vast variety of substances which we see is composed of a few simple bodies, which hence are called elementary substances.

Formerly, air, earth, fire, and water, were supposed to be the elements of which all bodies were formed ; but modern chemistry has shown that this was an erroneous supposition. For the air, or atmosphere, is compounded of several distinct kinds of aerial fluids or gases. Instead of one kind of earth, it is now known that there are several kinds. Water is no longer considered as an element, being, in fact, formed of two substances very different, viz. of oxygen and hydrogen. "Fire is less understood, and is still retained as an element under the name of caloric.

From the improvements that are continually

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