A Catechism of Familiar Things Part 31

What is meant by Ochreous?

Consisting of ochre, a kind of earth with a rough and dusty surface, composed of fine, soft, clayey particles, which readily separate in water. There are various colored ochres, as red, yellow, blue, green, &c.; they are very useful in many of the arts.

What term is used to denote the quality of the Diamond?

In speaking of the value of diamonds, we distinguish them as "diamonds of the first water," meaning those which possess the greatest perfection and purity, which ought to be that of the clearest drop of water: when they fall short of this perfection, they are said to be "of the second or third water," and so on till the stone may be properly called a colored one.

What is the Ruby?

A beautiful gem of a red color; in its perfect state it is of great value. The ruby is often found perfectly pure and free from all spots or blemishes; but its value is much more frequently lessened by them, especially in the larger stones. It is very hard, being second only to the diamond in this respect; and is often naturally so bright and pure on the surface as to need no polis.h.i.+ng; it is often worn in rings, &c., in its rough or native state. The color of rubies varies from the deepest to the palest red, all having more or less of a purplish tinge, which is more plainly perceived in the deeper colored specimens than in the paler ones.

Where are Rubies found?

They are mostly found in gold mines. We have the true rubies only from the East. The Isle of Ceylon has long been celebrated for these gems; they are found in a river which descends from the mountains; they are brighter and more beautiful than those obtained in other parts, but are very rare. Some crystals are frequently found tinged with the true color of the ruby, but these want its l.u.s.tre and hardness.

Describe the Emerald.

It is a precious stone of a beautiful transparent green color, and, when in a state of perfection, nearly equal to the ruby in hardness.

The finest and best are found in America, especially among the mountains of Peru; they are also obtained from a few places in the East. These gems are often counterfeited, as are most of the precious stones, there being even false diamonds; the genuine may be known by their extreme hardness and brilliancy.

_Counterfeited_, imitated with a view to defraud.

_Genuine_, true, real.

What is the Turquois?

A beautiful blue stone; it is one of the softest of the gems, and some varieties are often used for seals, as they admit of being engraved upon. The turquois is easily imitated, and that often so perfectly as to render it very difficult to distinguish the counterfeit from the true gem.

In what countries are they found?

The Oriental Turquois comes from Persia, the Indies, and some parts of Turkey; the turquois is also found in various parts of Europe, as Germany, Spain, and France.

What is Engraving?

The art of cutting metals or precious stones, and representing thereon figures, letters, and devices; the term is, however, more particularly applied to the art of producing figures or designs on metal, &c., for the purpose of being subsequently printed on paper. The ancients are well known to have excelled in engraving on precious stones; many specimens have been preserved, which surpa.s.s anything of the kind produced by the moderns. This art is frequently alluded to in the Bible. Engraving on wood, according to some authors, was introduced into Europe from China by Venetian merchants; it is certain the art was practised in eastern and northern Italy as early as the thirteenth century. The invention of copper-plate engraving has been ascribed to a goldsmith of Florence, about the year 1460.

_Device_, that which is formed by design.

_Design_, a representation of a thing by an outline; a sketch.

Describe Wood Engraving.

The subject is drawn on a block of box or pear-tree wood with a black-lead pencil, or with a pen and Indian ink; the wood is then cut away, so as to leave the lines which have been drawn, as raised parts.

The ink is next applied, and by pressing damp paper upon the block, the impressions are obtained. Albert Durer, a celebrated painter of Germany, brought the art of engraving on wood and metal, and taking off impressions on paper, &c., to great perfection.

How is engraving on copper, steel, &c., performed?

This sort of engraving is performed with a sharp-pointed instrument called a _graver_, by means of which figures, landscapes, &c., are traced upon a flat surface of the metal: the lines are then filled with ink or a similar composition, and the paper pressed on the plate.

When taken off, an exact copy of the plate is impressed upon its surface.

[Ill.u.s.tration: COCHINEAL INSECTS AND PLANTS.]

What is Lithography?

A species of engraving on stone, from which impressions can be taken much more expeditiously and economically than from metal. The process depends upon the following principles:--First, the facility with which calcareous stones imbibe water; second, the power of oily substances to repel water. When drawings are executed upon the stone with crayons composed of oily materials, and the surface of the stone is washed over with water, the moisture is imbibed by the stone, but repelled from the engraving; and when the ink, which also contains oily substances, is applied, it adheres only to the drawing, and not to the other portions of the stone. The block is then pa.s.sed through a press, and the impressions are taken off; as many as 70,000 perfect copies have been obtained from a single stone.

_Expeditiously_, with celerity or dispatch.

_Economically_, with economy; with frugality.

You describe Pearls as being ranked among the number of Gems, although they are not Stones; what kind of substance are they?

Pearls are excrescences found in the sh.e.l.ls of a large species of oyster, which are supposed to be produced by a disease of the fish.

The best pearls are generally taken from the most fleshy part of the oyster, near the hinge of the sh.e.l.l, but inferior kinds are found in all parts of the fish, and adhering to the sh.e.l.ls. Pearls, from many allusions made to them in the Old Testament, were not only known to the ancients, but were regarded by them as costly and precious gems.

How do they get the Oysters which contain them?

By diving under water and picking the oysters from the large beds at the bottom of the sea; or the rocks to which they adhere. The divers cast all the oysters they take into their boats, and carry them ash.o.r.e, where they deposit them in heaps; they are then left till they become putrid, this being necessary in order to remove the pearls easily from the rough matter by which they are surrounded.

What sea produces the best and greatest number of Pearls?

The finest and greatest quant.i.ties are obtained off the coast of Ceylon; the pearl oyster is also found in the seas of the East Indies; in those of America, and in some parts of the European seas; but these last are much inferior. The Oriental pearls are the finest on account of their size, color, and beauty, being of a silvery white; while the Occidental pearls are smaller, and frequently tinged with a yellow or blackish hue.

_Tinged_, slightly colored.

Does not the Pearl Oyster produce a substance called Mother-of-Pearl?

No; the beautiful substance so much used for inlaying boxes, and for ornamental knife-handles, &c., is produced from the sh.e.l.l, not of the pearl oyster, but of another sea-fish of the oyster kind.

What is Inlaying?

The art of ornamenting a plain surface of wood, or other material, with thin slices or leaves of a finer wood, of a different kind; as mahogany inlaid with ebony, &c., or with ivory, and other substances.

There are two kinds of inlaying; one, of the more ordinary sort, which consists only of compartments of different kinds of wood, inlaid with one another; the other, requiring greater skill, represents flowers, birds, and other figures. The thin plates of wood or other substance, being sawed into slips, and cut into the required forms, are carefully joined, and afterwards strongly glued down on the block of wood, &c., intended to be thus ornamented.