good to know, on occasion of scarcity, that gum, and all those vegetables, which, upon chewing, become slimy in the mouth, will afford an innocent nourishment. Some poor people, who dwell on the sea-shore, in cold countries, obtain food from certain kinds of sea-weed which abound in mucilage; and the Icelanders, in their inhospitable climate, derive great help from a kind of lichen or liver-wort, a leathery sort of substance growing on the ground, which yields a strong jelly when boiled in water or milk. It is imported into this country as a salubrious article of diet to the consumptive. But the most important by far of these mucilaginous products are gum-arabic and gumSenegal, two substances very closely resembling each other in all respects. Gumarabic was the first known in Europe; and Cairo and Alexandria were the principal marts for it, till the Dutch, about the beginning of the seventeenth century, introduced this gum into commerce from their settlements on the river Senegal, which now supply the greater part of our vast demand for this article, employed by us in calico

printing; and for many other manufacturing purposes. The tree which yields it, is a kind of thorny mimosa, growing abundantly on the sands along the whole of the Barbary coast. The trees are from eighteen to twenty feet high. Immediately after the heavy periodical rains, the gum is seen oozing spontaneously through the stem and branches, where it soon hardens in round lumps about the size of a partridge's egg. This harvest continues about six weeks. Besides the pur

poses for which it is exported, this gum also affords a very wholesome and nutritious food; thousands of the Moors live entirely upon it during the season of collecting it. Six ounces are accounted sufficient to support a man for a day. The caravans which cross the deserts of Arabia, with loads of gumarabic, when in want of provisions, have sustained life for many days on this sub

stance.

I believe I have now mentioned all the principal articles of vegetable food presented to us by nature. You see they are very numerous, and many of them easy to be procured, so that it would seem that there is

little danger of absolutely starving in a climate and soil where plants grow in profusion. But a mere casual supply would never provide for a considerable population; and is besides subject to much uncertainty and inconvenience. Human art, therefore, has in all countries employed certain methods to secure and improve these gifts of providence. What these are will make the subject of some of my future letters. But I will first take this opportunity to give you some account of a substance which, if not actually food itself, is the most general of all the condiments of food, one without which we should find onr meals tasteless; and even disgusting. It also contributes largely to the support of mankind, by preserving articles of animal food for future use, which would otherwise be spoiled and wasted. You will perceive that I mean salt.

This substance is very extensively diffused over the globe, but like most other mineral substances, valuable to man, it is seldom supplied to him by nature in a state fit for his purposes, without some labour or skilful efforts of his own. It is found sometimes as

rock salt, which is its purest native condition, sometimes mingled in small particles in certain rocky beds, sometimes in saltsprings, and lastly in sea water. In order to procure it in a state of purity and dryness, it is necessary to dissolve it and subject it to certain processes, even where it is found solid; and where it exists as brine, to evaporate the liquor till the salt which it contains forms into crystals. In weak brine, this effect is assisted by dissolving in it portions of rock salt. It is obtained in many warm countries from sea water, evaporated by the heat of the sun, in shallow pools, called salt pans; and some is procured by this method in our own country; but our grand reservoir of it is in the salt springs of Cheshire and Worcestershire. From all these sources, we manufacture, annually, not less than half a million of tons, mostly of the best quality, in part for exportation, and in part for our immense home consumption. With this we season vast quantities of cheese; with this we pickle thousands of casks of pork and beef for the use of our navy and merchant ships; and with this we cure

myriads out of the vast shoals of pilchards and herrings, which every year swarm around our coasts, to make the fasting diet of all the Roman catholic nations of the south of Europe. From our salt, we likewise extract soda, for the use of soap-boilers and glassmakers; and a substance called chlorine, indispensable in the modern art of bleaching fabrics of linen and cotton.

From the intense craving for salt felt by all mankind, who have ever known the taste of it, and even by many animals, especially those of the ruminating class, it is to be supposed that to all these it is salutary in moderation; yet it is noxious, and even fatal to all life, animal or vegetable, when received in large quantities; and this was, perhaps, the reason that among the ancients it was made the very symbol of barrenness and destruction. When a city, overthrown by an enemy, had been sown with salt, it was understood that it was never to be rebuilt; but to lie devoted to perpetual solitude and desolation. At the same time, a kind of sacredness was always attached to this substance. By the Mosaic law, every "meat