What is a Microscope?

An optical instrument, by means of which very minute objects are represented exceedingly large, and viewed very distinctly according to the laws of refraction or reflection. Nothing certain is known respecting the inventor of microscopes, or the exact time of their invention, but that they were first used in Germany, about 1621.

_Minute_, small, diminutive.

_Refraction_, a change in the direction of a ray of light, when it pa.s.ses through transparent substances of different densities.

_Reflection_, a turning back of a ray of light after striking upon any surface.

What is the Steam Engine?

A machine that derives its moving power from the force of the steam produced from boiling water, which is very great, especially when, as in the steam engine, it is confined within a limited compa.s.s: this useful machine is one of the most valuable presents that the arts of life have received from the philosopher, and is of the greatest importance in working mines; supplying cities with water; in working metals; in many mechanical arts; and in navigation. By the aid of steam, vessels are propelled with greater swiftness than those which are wholly dependent on the winds and tides; and thus trade is facilitated, and we are enabled to communicate with distant lands in a much shorter s.p.a.ce of time than was formerly consumed. On land, railroads are constructed, on which steam carriages run with astonishing rapidity, so that a journey which by coach and horses formerly required two or more days, may now be performed in four or five hours.

_Mechanical_, belonging to Mechanics.

To whom are we indebted for its invention?

Its invention is by most writers ascribed to the Marquis of Worcester, an Englishman, about 1663; but it does not appear that the inventor could ever interest the public in favor of this, or his other discoveries. The steam engine of Captain Savery, also an Englishman, is the first of which any definite description has been preserved. It was invented in 1698. Since that period it has been successively improved by various persons, but it is to Mr. Watt and Mr. Boulton, of England, that it is indebted for much of its present state of perfection.

By whom was the Steam Engine first applied to the purposes of Navigation?

By John Fitch, of Pennsylvania. From papers in the historical collections of Pennsylvania, it appears that the first successful experiments were made at Philadelphia, in 1785, three years before the attempts at Falkirk, and on the Clyde, in Scotland. The boat made several trips on the Delaware and Schuylkill rivers, but owing to repeated accidents to her machinery, and the want of funds and competent mechanics for the necessary repairs, she was abandoned. In 1807, Robert Fulton, also of Pennsylvania, made his first experimental trip on the Hudson River, with complete success. To this distinguished and ingenious American justly belongs the honor of having brought navigation by steam to a state of perfection. In 1819, the first steamship crossed the Atlantic from Savannah to Liverpool; and in 1838, a regular communication by steamship was established between Great Britain and the United States. Since that period, ocean navigation by steam-vessels has made rapid progress, and, at the present time, numbers of steamers connect our various seaports with those of other nations, and with each other.

What is the Electro-Magnetic Telegraph?

An instrument, or apparatus, by means of which intelligence is conveyed to any distance with the velocity of lightning. The electric fluid, when an excess has acc.u.mulated in one place, always seeks to transfer itself to another, until an equilibrium of its distribution is fully restored. Consequently, when two places are connected by means of a good conductor of electricity, as, for instance, the telegraphic wire; the fluid generated by a galvanic battery, if the communication be rendered complete, instantaneously traverses the whole extent of the wire, and charges, at the distant station, an electro-magnet; this attracts one end of a lever, and draws it downward, while the other extremity is thrown up, and, by means of a style, marks a slip of paper, which is steadily wound off from a roller by the aid of clock-work. If the communication is immediately broken, only one wave of electricity pa.s.ses over, and a _dot_ is made upon the paper; if kept up, a _line_ is marked. These dots and lines are made to represent the letters of the alphabet, so that an operator employed for the purpose can easily read the message which is transmitted.--The Electro-Magnetic Telegraph was first introduced upon a line between Baltimore and Washington, by Professor Morse, in 1844; at the present time, it is in successful operation between nearly all the important cities and towns of the United States and of Europe.

An _Electro-Magnet_ is a piece of soft iron, rendered temporarily magnetic by being placed within a coil of wire through which a current of electricity is pa.s.sing.

CHAPTER XIII.

SOAP, CANDLES, TALLOW TREE, SPERMACETI, WAX, MAHOGANY, INDIAN RUBBER OR CAOUTCHOUC, SPONGE, CORAL, LIME, CARBON, OXYGEN, NITROGEN, GAS, HYDROGEN, CHALK, AND MARBLE.

Of what is Soap composed?

Of soda or potash, and various oily substances; it is so useful for domestic and other purposes, that it may be regarded as one of the necessaries of life; immense quant.i.ties of it are consumed in all civilized countries. Soft soap is generally made of a lye of wood-ashes and quicklime, boiled up with tallow or oil; common household soap of soda and tallow, or of potash and tallow; when potash is used, a large portion of common salt, which contains soda, is added to harden it. The finest white soaps are made of olive oil and a lye consisting of soda and quicklime; perfumes are sometimes added, or various coloring matters stirred in to give the soap a variegated appearance. The ancient Greeks and Hebrews appear to have been acquainted with the art of making soap, or a composition very similar to it; and also the ancient Gauls and Germans. A soap-boiler's shop, with soap in it, was found in the city of Pompeii, in Italy, which was overwhelmed by an eruption of Mount Vesuvius, A.D. 79.

What is Soda?

Soda, or barilla, is obtained from the ashes of marine plants, and by the decomposition of common salt; its great depository is the ocean, soda being the basis of salt. The marine plants from which the soda is obtained, are endowed with the property of decomposing the sea-salt which they imbibe, and of absorbing the soda which it contains. It is found native in Egypt, and is there called _natron_; a name similar to that which it bore among the Jews and Greeks.

_Depository_, store-house, place where anything is lodged.

_Imbibe_, to drink in, to absorb.

Of what are Candles made?

Of Tallow, which means animal fat melted and clarified, that is, cleansed or purified from filth. Tallow is procured from many animals, but the most esteemed, and the most used, is that made from oxen, sheep, swine, goats, deer, bears, &c.; some of which tallows or fats are used in medicine, some in making soap, and dressing leather; others in the manufacture of candles, &c. For the last-mentioned article, that of sheep and oxen is most used; candles of a better sort are likewise made of wax and spermaceti. Candles are kept burning by means of a wick of cotton or rush, placed in the centre of the tallow, which is moulded into a cylindrical form.

_Cylindrical_, having the form of a cylinder.

Is there not a tree which yields a vegetable Tallow?

Yes; China possesses a tree producing a substance like our tallow, of which the Chinese make their candles; this tallow is extracted from the stone of the fruit, the tallow being a white pulp which surrounds it. In America, likewise, there is a shrub, a native of the temperate parts, especially towards the sea-side, the seeds of which contain a waxy substance used for the same purpose, and which is extracted by boiling; this shrub is a species of myrtle, and does not attain to any great size.

_Extracted_, drawn from.

What is Spermaceti?

A whitish, flaky, unctuous substance, prepared from an oil of the same name, drawn from a particular kind of whale, distinguished from the common whale by having teeth, and a hunch on its back.

_Flaky_, having the nature of flakes.

What is Wax?

A soft, yellow, concrete matter, collected from vegetables by the bee, of which this industrious and useful insect constructs its cell.

Wax forms a considerable article of trade; it is of two kinds, the yellow and the white; the yellow is the native wax as it is taken from the hive, and the white is the same washed, purified, and exposed to the air.

_Concrete_, grown together, solid.

What Tree produces the beautiful and well-known wood so much used in making the various articles of household furniture?

The Mahogany Tree, growing in America, and the East and West Indies; it frequently grows in the crevices of rocks, and other places of the same description. This wood was not used for making furniture till near the end of the seventeenth century. A London physician had a brother, the captain of a West India ship, who, on his return to England, having on board several logs of mahogany for the purpose of ballast, made him a present of the wood, he being engaged in a building project; his carpenter, however, threw it aside, observing that it was too hard to be wrought. Some time after, the lady of the physician being in want of a box to hold candles, the cabinet-maker was directed to make it of this wood; he also made the same objection, and declared that it spoiled his tools. Being urged, however, to make another trial, he at length succeeded; when the box was polished, the beautiful color of the wood was so novel, that it became an object of great curiosity. Before this time, mahogany had been used partially in the West Indies for ship-building, but this new discovery of its beauty soon brought it into general use for making furniture.

_Crevice_, a rent, a crack.

_Ballast_, the heavy matter placed in the hold of a vessel to keep it steady.

What is India Rubber or Caoutchouc?

An elastic, resinous substance, produced from a tree, growing abundantly at Cayenne, Quito, and other parts of South America; and also in some parts of the Indies. The tree which produces it is large, straight, and about sixty feet high. There is, however, a small species found in Sumatra and Java, and some of the neighboring islands.