portion is once formed, which is woven every year by the wondrous machinery set to work for this purpose, it receives no fresh texture, yet each fibre remains a conducting tube to transmit the sap upwards, or, in the course of time, becomes charged with various principles, prepared, as already stated, by the leaves, and returned to the central part by that apparatus or system of canals for their transit inwards, the medullary rays, and at last are obstructed, so that no passage of fluid is effected through the inner layers of wood. But for every layer that is thus blocked up, a new one, which will continue pervious, is formed exterior to those already existing, so that a constant provision is made for carrying on the vital processes; to accomplish which, a free channel from the points of the roots to the surface of the leaves is absolutely necessary. The outer strata, produced by a tree of considerable age, are observed to be thinner than those formed at an earlier period, and become successively thinner and thinner, so that ultimately, if accident should not have previously caused it, the death of the tree is inevitable. The portions which are obstructed constitute the duramen or heartwood, the pervious portion the alburnum or sapwood. The original tissue is colourless; but according to the nature of the secretions deposited in it, the heartwood is either of a deeper colour, sometimes party-coloured, or at least of a much greater specific gravity than the sapwood. The removal of the juices by any solvent restores the wood to its primitive hue, and renders it again light. The difference of weight of a cubic foot of wood depends not merely on the different quantity of vegetable tissue compressed into a given space, in the first construction of the tree, but also on the quantity and quality of the secretions ultimately lodged in it. The same species of tree will present a difference in this respect, according to the country or situation where it grew, and also according to the character of the seasons during the time it flourished. According to the nature of the tree, if placed in favourable circumstances in reference to soil and weather, it invariably prepares and lodges in the stem those principles which it was designed to elaborate—the oak preparing tannin—the sugar-maple preparing its saccharine juice. That the primary object of these was some advantage to the tree itself can scarcely be doubted, but the secondary applications of which they are capable, give reason to suppose that these also were contemplated in their formation. The consideration of the means by which they are formed, and the direct consequences of their formation on the air, by abstracting certain elements from it, and supplying others, belong to the subject of leaves; it is the object of the present paper to view them as formed, and to show their amazing utility.

The mechanical properties of the stems of trees, both exogenous and endogenous, render them extremely serviceable to mankind. The uses to which a single species of plant may be put are numerous and important, of which the reed (arundo phragmites) is an example, for after the root has assisted in binding and consolidating the soil, the stem is susceptible of the most varied applications[A].

In a low state of civilization the palm, or a palm-like grass, supplies all that man requires; of the former of which, the Mauritia flexuosa, or sago-palm of the Oronooko, and still more the cocos nucifera, or cocoa-nut palm; and of the latter, the bamboo (bambusa arundinacea, and other species) are proofs. The bamboo suffices for all the needs of the humbler Chinese; even their paper, as well as their abodes, are made of it; and from the materials furnished by the cocoa-nut tree, not merely food, as shall be afterwards noticed, but larger and more elegant houses, with all their appurtenances, are constructed at Goa and other places. The obligations of the Guaraons to the Mauritia flexuosa cannot be expressed[B]. In proportion as man rises in civilization, the importance of timber becomes greater, being a material for which no adequate substitute can be found. It combines lightness with strength, elasticity with firmness, and possesses in many instances a durability rivalling, or even surpassing, that of the rocks yielded to us by the solid substance of the globe. The adaptation of timber to the numerous wants of civil life is too familiar to require exposition; but in addition to all the ends it serves in these points, we have an interesting view presented to us in considering what a vast quantity of timber is required for the construction of our shipping, from the countless boats and small craft employed in our coasting trade up to the larger ships, which are so many floating towns or communities. These conduce to the accomplishment of objects of the most momentous nature. Were it not for our shipping we should still be in the condition described by the Romans, as Britons cut off from the rest of the world.—But by their means we now visit without restraint,

and though, in times past, they have been too often used as engines fraught with destruction, directed by man against his fellow man, let us hope that they may be required in future only to convey in amicable interchange the produce of one country to another, or to bear to his destination the missionary bent on extending the blessings of that religion whose spirit is “peace on earth, good will among the children of men[D].”

As a means of supplying fuel, without which man must remain constantly in the savage state, wood is of inestimable value. In the process of combustion, the elements of the trees enter into new combinations, evolving both light and heat, which at once maintain life and render it a state of enjoyment and usefulness. For this purpose in Britain, we chiefly employ fossil fuel, stored up in the secret places of the earth, and, therefore, we attach less importance to recent wood; but other parts of the world are not so favourably situated, and to the inhabitants of these places fresh, or but lately felled, wood is necessary for their existence. Even in France, though partially possessed of coal, it is estimated that the quantity of wood employed to supply heat, whether for comfort, cooking, or in manufactures which require a high temperature, amounts to seven-tenths of the entire consumption. The superiority of wood fuel, whether fossil or recent, over every other material resorted to with a like intention, shall be shown in a subsequent part of this paper. I therefore pass on at present to demonstrate the utility of vegetable substances in affording the means of subsistence to man and animals.

In the observations I am about to make, it is impossible to avoid anticipating some of the remarks which belong to the subject of fruits and seeds as articles of food, since the same principles of nutriment are found in the stems of certain plants as are deposited in the fruits or seeds of others.

Though man is omnivorous, and can subsist either on animal or vegetable food—an