صور الصفحة
PDF
النشر الإلكتروني

among the solid strata of the earth, and which have been constantly quarried through successive ages from the earliest records of history, the ocean itself is a never failing source of this valuable substance. In other instances salt springs afford the means of a ready supply: and, throughout a considerable part of the sandy districts of Africa and Asia, the soil itself abounds with it.* . The abundant supply of common salt coincides with its extensive utility. It is every where indispensable to the comforts of man; and it is every where found, or easily obtained by him. And, though not to the same extent, the same observation holds with reference to many other natural saline compounds. Thus carbonate of potash, and natron or carbonate of soda, alum, borax, sal ammoniac, and sulphate of iron, or green vitriol, which are most extensively useful salts in many processes of the arts, are either found abundantly in various parts of the world, or may be obtained by very easy means: while a thousand other saline compounds, which are rarely of any practical importance, are scarcely known to exist in a native state. And it is probable that that useful metal, copper, in consequence of its frequent occurrence in a native state, was employed long before the mode of reducing iron from its ores had been discovered; as Werner (and Hesiod, and Lucretius, ages before him”) conjectured.

* It does not belong to our present purpose to describe the common processes by which the salt is obtained either from the sea, or from any other liquid that may hold it in solution: but the following account of a particular process, for this purpose, so well illustrates the ingenuity of the human mind in taking advantage of natural hints, if the expression may be permitted, that no excuse can be necessary for its introduction. In Guiana there is a very common species of palm, the flowers of which are enveloped by a sheath capable of holding many pints of water; and the density and general nature of the sheath is such, that the water contained in it may be heated over a fire without destroying its substance: and the Caraïbs actually employ these sheaths, in evaporating the sea water for the purpose of obtaining a quick supply of salt. (Diction. des Sciences Nat. tom. xxxvii.

p. 283,

CHAPTER VIII.

ADAPTATION OF VEGETABLES TO THE PHYSICAL CONDITION OF MAN.

SECTION I. General Observations on the Vegetable Kingdom.

THE vegetable kingdom has this distinction with reference to the subject of the present treatise, that its productions are among the first objects that forcibly attract the attention §. children; becoming to them the source of gratifications, which are among the purest of which our nature is capable; and of which even the indistinct recollection imparts often a fleeting pleasure to the most cheerless moments of after-life.

Who does not look back with feelings, which he would in vain attempt to describe, to the delightful rambles which his native fields and meadows afforded to his earliest years? Who does not remember, or at least fancy that he remembers, the eager activity with which he used to strip nature's carpet of its embroidery, nor ceased to cull the scattered blossoms till his infant hands were incapable of retaining the accumulated heap! Who, on even seeing the first violet of returning spring, much more on inhaling its sweetness; or in catching the breeze that has passed over the blossom of the bean or of the woodbine, does not again enjoy the very delights of his early childhood 7

* xxxx; 3' eyāčerre, oxas 3’ or irks one's.
EPT. KAI HM. line 15 1.
Posterius Ferri vis est, Ærisque reperta.
Et prior AEris erat quam Ferri cognitus usus.
LUCRET. W. 1285.

It may be said indeed that the pleasure of such recollections is for the most part of a moral and intellectual nature; and, so far, is foreign to our present object; but the pleasure of the original enjoyment appears to be principally of a physical character; and is no doubt intended to produce, at the moment, a highly beneficial, though merely physical effect: for while the eye of the child is attracted by the unexpected forms and colours of the plants and flowers presented to his view, and his mind is instigated to gratify the eager desire of possessing them, he necessarily subjects his limbs to that degree of exercise and fatigue, which contributes to the general health of his body. Nor let such pleasures be undervalued in their consequence: they give that moderate stimulus to the whole system, which even the early age of infancy requires; and, by shutting out the listlessness that would arise from inactivity, they become eventually the source of moral and intellectual improvement.

With reference to the primary wants of mankind at large, the vegetable kingdom is of the highest importance. Let the earth cease to produce its accustomed fruits, and every form of animal life must be soon annihilated: for all animals either derive their nourishment directly from vegetable food, or feed on those animals which have themselves fed on vegetables. And, without the aid of the same productions, we should be deprived of various substances which are now employed for clothing, and fuel, and the construction of our habitations. But the adaptation of the vegetable kingdom to the arts and conveniences of life is visible in numerous other instances: and the principal difficulty, in illustrating this point, is the selection of appropriate examples, and the order of their arrangement.

SECTION II.

The Cocoa-nut Tree, including the formation of Coral Reefs.

For the purpose of introducing in a more particular manner the general subject of this chapter, and as an impressive example of the important ends which nature often accomplishes by the simplest means, I propose to consider the mode in which the cocoa-nut tree is spontaneously propagated in the coral islands of the Indian Archipelago and elsewhere: nor will it be an undue anticipation of a subsequent department of this treatise, if I previously give a brief description of the process by which those islands have themselves been brought into existence. The account of their origin indeed belongs more strictly to the history of the animal than of the vegetable world; but the two subjects are so naturally connected, that it would be injudicious to separate them.

It may be collected from the observations of the French navigator, M. Péron, (Ann. du Mus. tom. vi. p. 30, &c.) that almost all those countless islands of the Pacific Ocean, which are found to the south of the equator between New Holland and the western coast of America, are either entirely or in part made up of coral: and all the adjacent ocean abounds with coral reefs, which, constantly augmenting, are constantly changing the state of bays, and ports, and gulfs; so that new charts are continually required for the same coasts. From Barrow also it appears, (Barrow's Cochin China, p. 167,) that the formation of coral reefs or isles is very common in the tropical parts of the Eastern and Pacific Ocean. And Captain Flinders says that the quantity of coral reefs between New Holland and New Caledonia and New Guinea, is such, that this might be called the Corallian Sea. (Flinders's Voyage, vol. ii. p. 314.)

Many more references might be made, to others as well as the above mentioned voyagers, in order to show that the formation of coral islands is effected by nature on a very extensive scale: but, for the present purpose, the preceding references may be considered sufficient. Let us now therefore describe the general character and mode of formation of these islands.

Forster says” that the low islands of tropical seas are commonly “narrow, low ledges of coral rock, including in the middle a kind of lagoon; and having here and there little sandy spots, somewhat elevated above the level of high water, on which cocoanuts thrive:” correspondent with which description is the account given by Captain Cook, on the occasion of discovering one of these coral reefs; which was at first mistaken by him for land. “This proved to be,” he says, “another of those low or half-drowned islands, or rather a large coral shoal, of about twenty leagues in circuit. A very small part of it was land, which consisted of little islets ranged along the north side, and connected by sand banks and breakers. These islets were clothed with wood, among which the cocoa-nut trees were only distinguishable. We ranged the south side of this shoal at the distance of one or two miles from the coral bank, against which the sea broke in a dreadful surf. In the middle of the shoal was a large lake, or inland sea, in which was a canoe under sail.” (Cook's Voyage, 4to. 1777. vol. i. p. 141, 142.)

Coral, considered as an individual substance, is a natural form of carbonate of lime, produced by an animal of the polype kind. The particles of carbonate of lime, however produced, are cemented together so firmly by a glutinous secretion of the same animal, as to acquire a degree of consistence, which not only forms a safe habitation for a race of animalcules, from their soft texture most obnoxious to

* Forster's Voyage round the World, p. 14, 15.
O

« السابقةمتابعة »