A Catechism of Familiar Things Part 18

What is Alum?

A kind of mineral, of a strong, sharp taste. It dissolves both in cold and boiling water, but best in the latter. It is of some use in medicine; a princ.i.p.al ingredient in dyeing and coloring, neither of which can be well performed without it, as it sets and brightens the colors, and prevents them from washing out. It is also extremely useful in many arts and manufactures.

Are there not different sorts of this material?

The princ.i.p.al kinds are native alums: _viz._ those prepared and perfected underground by the spontaneous operations of nature; as the roch, commonly called rock alum, from Rocha, in Syria, whence it is brought.

_Spontaneous_, una.s.sisted by art.

_Orientals_, inhabitants of the Eastern parts of the world.

What is Ink?

A liquor used in writing on paper or parchment, made of copperas, galls; and gum arabic[6] mixed together. There are likewise several plants that may serve for the making of ink, as oak-bark, red roses, log-wood, &c. It is also made from an infusion of oak galls and iron filings: there are also many other ways, as well as materials, employed in the making of this useful article. Ink is the name applied to all liquids used in writing, of whatever color they may be, as red, blue, &c., though black is the most used for common purposes. The ink of the ancients seems to have been of a thick, oily nature, unlike the modern ink; it consisted of nothing more than a species of soot, or ivory black, mixed with one fourth of gum.

[Footnote 6: See Chapter XI.]

What is Copperas?

A kind of vitriol. Copperas is the name given to green vitriol, which is a preparation from iron. The blue vitriol is a sulphate of copper, and the white vitriol a sulphate of zinc.

For what is Vitriol used?

In the making of gla.s.s, to color it; in many arts and manufactures; and in medicine.

What are Galls?

Excrescences formed on a kind of oak tree in certain warm climates; perforations are made by an insect into the bark of the tree, whence issues a liquid which hardens by exposure. They are used in dyeing, making ink, and other compositions. There are two sorts of oak galls in our shops, brought from the Levant, and the southern parts of Europe.

What does the word Levant signify?

A country to the eastward. It is applied to the countries of Turkey, Greece, Asia Minor, Syria, Egypt, &c., which are washed by the eastern part of the Mediterranean.

Is the Ink used in Printing the same as writing Ink?

No; it is more of the nature of paint, being thicker and more glutinous: it chiefly consists of a mixture of oil and lamp-black, or some other ingredient, according to the color required; and is remarkable for the ease with which it adheres to paper that is moistened.

_Glutinous_, gummy, resembling glue.

What is Indian, or Chinese Ink?

An admirable composition, not liquid like our ink, but solid, and made into cakes somewhat like the mineral colors we use in painting. It is made into all sorts of figures, usually long, and about an inch thick; sometimes gilt with the figures of birds, flowers, &c. To use this ink, it must be rubbed with water, on stone or earthenware, till it produces a beautiful, liquid, shining black. It is used in drawing, &c., and is brought from China. It is composed of lamp-black and size, or animal glue, or gum, to which perfumes and other substances are sometimes added.

CHAPTER X.

ASBESTUS, SALT, COAL, IRON, COPPER, BRa.s.s, ZINC, AND LAPIS CALAMINARIS.

What is the name of the remarkable stone of which a cloth has been made, that resists the action of fire?

The Asbestus, a mineral substance of a whitish or silver color. There are several species of this mineral, which are distinguished by different names, according to the appearance of each, as fibrous asbestus, hard asbestus, and woody asbestus; it is the fibrous sort which is most noted for its uses in the arts. It is usually found inclosed within very hard stones; sometimes growing on their outside, and sometimes detached from them.

_Fibrous_, full of fibres or threads.

What are its qualities?

It is insipid; will not dissolve in water; and exposed to the fire, it neither consumes nor calcines. The industry of mankind has found a method of working upon this untoward mineral and employing it in making cloth and paper; the process is, however, difficult.

_Insipid_, without taste.

Was not this curious mineral better known to the ancients than it is at present?

The linen made from it was highly esteemed by them; it was not only better known, but more common, than among us, being equally valuable with the richest pearls; but the superiority of all other cloths to this in every respect, except the resistance to fire, has caused incombustible cloth to be regarded in modern times merely as a curiosity, but it is still employed in chemical preparations.

_Incombustible_, remaining undestroyed in fire.

To what use did they put it?

In royal funerals, it formed the shroud to wrap the body in that its ashes might be prevented from mingling with the wood, &c., that composed the pile. Some of the ancients made themselves clothes of it, particularly the Brahmins among the Hindoos; it formed wicks for their perpetual lamps; thread, ropes, nets, and paper were also made of it.

Pliny, the Roman naturalist, says he has seen napkins of asbestus taken soiled from the table after a feast, which were thrown into the fire, and by that means better scoured than if they had been washed with water.

_Naturalist_, a person who studies nature, especially in what relates to minerals, vegetables, and animals.

_Brahmins_, Hindoo priests.

Where is the Asbestus found?

This mineral is found in the greatest quant.i.ty in the silver mines of Saxony; at Bleyburg, in Carinthia; in Sweden, Corsica, and sometimes in France, England, and the United States; also in Tartary and Siberia.

What method is used in preparing the Asbestus?