Obrázky na stránke
PDF
ePub

their nature, that neither will the moth touch, nor water rot them. To facilitate this union, the skins are placed in pits with large quantities of bark containing the necessary tannin,—water also being largely added to dissolve it. After lying a considerable time, the skin takes up a sufficient quantity of the tannin, and becomes Leather.

The most valuable bark for this purpose in our own country, is that of the oak. The Dutch and Belgians also send us very large quantities of oak bark, which is stripped from the trees when they are felled for their timber, and chopped into small pieces. We also use the bark of the larch tree, but it is not so powerful an agent as that of the oak.

In Turkey, they have a very small oak, which, though not growing larger than an elder-bush, produces large acorns, the cups of which are extremely curious, on account of their being covered over with woody scales. These cups are much prized by tanners, and our merchants import very large quantities under the name of Valonia. 1 The shells of the pomegranate fruit have also the property of tanning, and in Barbary, they are used for making the celebrated Morocco leather. In Russia, the bark of the birch is employed, and owing to its containing a strongly scented oil, the leather made with it always possesses an agreeable smell.

From South America we obtain, in vast quantities, a curious brown seed-pod, which is of great use to the tanners.

It is somewhat like a pea, but bent in the form of the letter S, of a darkbrown colour, and goes by the name of Divi Divi, a name which it probably received from the Indians, but which our merchants have adopted.

The Cork-tree-oak bark also is sent from Northern Africa, Acacia bark from India, and Mangrove bark from Sierra Leone, all to be used in tanning. But the most important of all the substances imported for this purpose is Catechu, which is made by cutting up the wood of a certain species of Acacia into chips, and boiling it until it makes the water a dark-brown colour ; then straining off the water from the chips, and boiling it by itself, until nothing remains except the brown colouring matter, which soon becomes hard and brittle. Having been packed in mats, it is sent from the East Indies to this country in very large quantities. This material is differently prepared in different parts of India, and, consequently, there are several sorts, known to our merchants by the names of Catechu, Terra Japonica, Cutch, and Gambier. These materials, being easily dissolved in water, tan skins very rapidly ; but the leather is not so good or durable as that which is more slowly prepared by oak-bark.

1 Sometimes they are gathered when very young, and not fully formed; they are then called Camata or Camatina. In this state they are more valuable, but too expensive to be much used.

A kind of fruit, not unlike a large acorn, but wrinkled instead of smooth, is also imported from India, to be used in our tan-pits, as well as in our dyeing-vats. It is called Myrobalan. The best Myrobalans are gathered before they are ripe, and they become wrinkled in drying.

All these materials derive their value from the fact that they contain the substance called tannin, and from the power which it has to unite with the animal skin, and thus form leather. Leather is thus a chemical compound, formed by the union of tannin with that part of the skin which is called albumen (which we see nearly pure, and in a hardened state in our finger nails), and, accordingly, if we were to use chemical language in describing leather, we should call it tannate of albumen.

VII. ON THE MATERIALS USED FOR PERFUMERY.

The exquisite pleasure we enjoy from the smell of sweet flowers is alone sufficient to account for the love of perfumery. Flowers pass away so quickly, that we naturally desire to preserve their sweetness as long as we can, and in accomplishing this, our perfumers succeed admirably. It happens that the perfume of most flowers depends upon the presence of an oil, which is peculiar to the plant, almost every sweet-scented plant having its own particular oil : and what is of more importance, these oils belong to a class called essential or volatile, because they become volatile, or evaporate, when heated. The common or fixed oils, on the contrary, such as olive or linseed, will not evaporate. This may be easily illustrated, thus : if a piece of writing-paper be touched with a fixed oil, or grease, it leaves a stain, which, if held to the fire, remains not only permanent, but spreads considerably. If, however, the paper is touched with an essential oil, it will make a similar stain, which, upon being held before the fire, will disappear altogether. Now, if any plant has a particular smell or taste, it is generally found that its essential oil is the cause of this ; and that, consequently, if we extract this we really obtain the essence. For instance, if we distil the herb known as peppermint, we obtain an essential oil, which both smells and tastes of peppermint, and thus we can retain, as long as we please, the essential principle which made the herb valuable to us, whereas the herb itself grows up, and perishes within a year.

The general method used for obtaining the essential oil is to put the leaves, flowers, or other parts of the plant, the perfume of which we wish to obtain, into a large distilling apparatus, mixing them with water. When the water boils, the steam which passes off contains portions of the volatile oil. This steam is then condensed, or re-converted into a liquid, by being passed in pipes through cold water. The water, thus condensed from the steam, has the essential oil floating on it, as a greasy film gradually increasing in quantity. This is skimmed off, and afterwards purified by filtering. Sometimes, if the vegetable material from which the oil has to be extracted is very perishable, salt is added, which does not affect the oil. In this way we distil perfumed essential oils from

The flowers of the Rose.
The flowers of the Lavender plant.
The leaves, rind, and flowers of the Orange and Lemon.
The leaves of the Rosemary.
The rind of the Bergamot Orange.
The spices called Cloves, Allspice, Nutmeg, Cinnamon, Cassia,

and various other materials. That from the Rose is called Attar, Utter, or Otto of Roses.

Herbs also, when properly dried, are used in perfumery : for instance, the roots of a species of Iris are prepared, and sold under the name of Orrice-root, and are used to give the odour of violets, which they possess in great strength. The shavings and sawdust of sandal-wood, a beautiful perfumed wood which comes from India, are often used.1 The leaves of an Indian plant yield the curious perfume called Patchouli, and the South American seed called Tonquin or Tonka-bean is used by tobacconists for scenting snuffs.

The gums yielded by some plants are also used in perfumery, as 1 The root of an Indian grass is sold under the name of Khus-Kbus, and has nearly the

gaine odour as the sandal wood.

Gum Benzoin, also called Benjamin, Gum Myrrh, and a few others.

The usual method of using these materials is to put them in very pure and scentless spirit. Spirit of wine or alcohol is employed for this purpose, and as it dissolves the essential oils and gums, and takes up their perfumes, it is well adapted for the purpose. Thus, Lavender Water, as it is called, is merely a spirit scented with various perfumes, of which oil of lavender is the principal

There are also two or three substances used in perfumery which we obtain from animals, as Musk, Civet, and Ambergris, but these belong to another branch of economic science.

The oily character of most perfumes enables us to scent oils, pomades, &c., in great perfection. Indeed, oils so readily, take up the perfume of plants, that they become scented merely by having the flowers placed near them, and this method is employed where the true essence cannot be obtained by simple distilling. Orange and jessamine flowers, for instance, are often placed between pieces of cotton-wool soaked in oil ; in a short time the oil becomes strongly scented, and answers well for hair-oils and pomatums.

SOCIAL SCIENCE.

1. Schoolmaster. I want to engage you boys on a new subject : I want you to begin the study of Social Economy, a branch of Social Science.

A Boy. Social economy ! What is social economy? what is the use of it to me ?

S. I am glad you ask me these questions, for a boy ought, before he gives up any considerable portion of his school-time to a new subject, to ascertain, as well as he can, both what it is he is about to work at, and that his work is likely to make him, in all respects, a more useful—a better man. But I cannot make my answer very short. If you will think along with me for a moment you will see that I cannot. Suppose some little boy who had not had the advantage of instruction in arithmetic, were to hear that you are learning at school to work Proportion. He would like to understand what Proportion is ; and you, if your school-training have rightly moulded your character, as well as informed your mind, will be willing and anxious to give him such an answer as he can understand. You, possibly, if your schoolmaster asked the question, could promptly give him the short and proper answer, which your text-books of arithmetic and algebra contain. But to your little untaught acquaintance, when he says seriously to you, as if he had full trust both in your knowledge and your kindness, “What is Proportion, and what's the good of it ?" the answer which well pleased your schoolmaster would be useless. If you would really give him help you must be at some pains, first of all, to find out what he does know, and then, by adapting your teaching to his knowledge, to lead him to discover what as yet he does not know. And some such course I must take with you, hoping that you will show me that attention and patience which you would like your young friend to show you.

« PredošláPokračovať »