A Catechism of Familiar Things Part 20

_Residuum_, the remaining part, that which is left.

_Antiseptic_, that which prevents putrefaction.

What is Iron?

One of the most useful and abundant metals; being found in all mineral earths, and stones; in plants, and animal fluids; and is the chief cause of the varieties of color in all. Iron is found in great ma.s.ses, in various states, in the bowels of the earth; it is usually, however, compounded with stone, from which it is separated by the action of fire. In some parts of the world, whole mountains are formed of iron; among these may be mentioned the Pilot k.n.o.b and the Iron Mountain, in Missouri, being unsurpa.s.sed by anything of the kind found elsewhere.

What are its characteristics?

It is hard, fusible, not very malleable, but extremely ductile, and very tenacious; it is of a greyish color, and nearly eight times heavier than water. Without iron, society could make no progress in the cultivation of the ground, in mechanical arts or trades, in architecture or navigation; it is therefore of the greatest use to man. Iron tools have been used in all European countries as long as their histories have existed; this metal appears likewise to have been known and used by the inhabitants of the world in the earliest ages, being frequently mentioned in the Holy Scriptures. In the fourth chapter of Genesis, Tubalcain is spoken of as "a hammerer and artificer in every work of bra.s.s and iron," and thus their existence was evidently known at that early period of the world.

_Artificer_, one who works or makes.

_Fusible_, capable of being melted by fire.

[Ill.u.s.tration: THE SALT MINES OF WIELICZCA.]

What do you mean by Metals?

Useful substances dug from the bowels of the earth, being sometimes found pure, but mostly combined with other matter. They are distinguished by their weight, tenacity, hardness, opacity, color, and peculiar l.u.s.tre, known as the metallic l.u.s.tre; they are fusible by heat, and good conductors of heat and electricity; many of them are malleable, and some extremely ductile. Those which were first known are gold, silver, iron, copper, mercury, lead, and tin.

_Tenacity_, the firmness with which one part adheres to another.

_Opacity_, want of transparency or clearness.

What are Metals called in their natural state?

Ores; so named because the metal contained in them is either mixed with other metals, or with mineral earths, from which they are separated and purified by various means: such as washing, roasting, &c., but the method is always regulated by the nature of the ore.

What is Copper?

A hard, heavy, ductile metal, found native, and in many ores; of these the most important is _copper pyrites_, which is a sulphuret of copper. Next to gold, silver, and platinum, copper is the most malleable and ductile of metals; it may be drawn into wires as fine as hair, or beaten into leaves as thin as those of silver. The rust of copper is very poisonous. Copper, mixed with a certain quant.i.ty of tin, forms bell-metal. With a smaller proportion, it forms bronze, a substance used in sculpture for casting figures and statues. It is an abundant metal, and is found in various parts of the world. Native oxides of copper are found in Cornwall, Siberia, and in North and South America.

_Oxide_, a substance combined with Oxygen,[8] in a proportion not sufficient to produce acidity.

_Sulphuret_, a combination of sulphur with a base.

[Footnote 8: See Chapter XIII., article Oxygen.]

What are the uses of Copper?

They are too various to be enumerated. In sheets it is much used to sheathe the bottoms of ships, for boilers, and other utensils. Copper coin was the only money used by the Romans till the 485th year of their city, when silver began to be coined. In Sweden, houses are covered with this metal.

What is a Mine?

A cavity under ground, formed for the purpose of obtaining metals, &c.; mines are often very deep and extensive. The descent into them is by a pit, called a shaft; the clues by which mines are discovered, are, mineral springs, the discoloration of vegetables, the appearance of pieces of ore, &c.

_Clues_, signs or means by which things hidden are brought to light.

What is Bra.s.s?

A fact.i.tious metal, consisting of copper and zinc. Bra.s.s is lighter and harder than pure copper, and less subject to rust; owing to these properties, together with its beautiful color, it is extremely useful in the manufacture of many utensils.

_Fact.i.tious_, made by art, not found in a natural state.

What is Zinc?

A metal of a brilliant bluish white color. Its name was unknown to the ancient Greeks and Arabians. It is mixed with other substances in the ore, from which it is obtained by smelting in the furnace. It has never yet been found native or pure.

For what is Zinc used?

From its readiness to dissolve in all acids, and unite with other metals, it is used in alloy with them in the composition of bra.s.s, &c.

Thin sheets of zinc are also used to cover roofs of houses, and in the manufacture of various household utensils.

What is Lapis Calaminaris?

Lapis Calaminaris, or calamine stone, is a native carbonate of zinc, of some use in medicine, but chiefly in founding. It is, sometimes brownish, as that found in Germany and England, or red, as that of France. It is dug out of mines, usually in small pieces; generally out of those of lead. Calamine is mostly found in barren, rocky soils.

_Founding_, the art of casting metals.

CHAPTER XI.

YAMS, MANGOES, BREAD-FRUIT, SHEA OR b.u.t.tER TREE, COW TREE, WATER TREE, LICORICE, MANNA, OPIUM, TOBACCO, AND GUM.

What are Yams?

The roots of a climbing plant growing in tropical climates. The root of the yam is wholesome and well-flavored; nearly as large as a man's leg, and of an irregular form. Yams are much used for food in those countries where they grow; the natives either roast or boil them, and the white people grind them into flour, of which they make bread and puddings. The yam is of a dirty brown color outside, but white and mealy within.

What are Mangoes?

The fruit of the Mango Tree, a native of India and the south-western parts of Asia; it also grows abundantly in the West Indies and Brazil.

It was introduced into Jamaica in 1782; where it attains the height of thirty or forty feet, with thick and wide-extended branches. The varieties of the mango are very numerous,--upwards of eighty are cultivated; and the quality of these varies according to the countries and situations in which they grow. The mangoes of Asia are said to be much better than those of America.