stances; and yet the most skilful and enlightened men differ about the best modes of preparing timber for ship building. Some recommend particular periods for felling the trees, as connected with the season of the year, or the age of the moon: some season their timber under sheds, others in the open air some cure it with artificial heat, kept up uniformly to a certain degree of the thermometer: some saturate it with chemical mixtures: some char the wood by burning, and others again immerse it for a time in water, either salt or fresh, in order to expel the sap. This latter mode of treating timber has for some time past been more especially practised; and immersion in salt water, particularly, has hitherto been deemed, by experienced men, as salutary. The opinion of the Commissioners is decidedly opposed to this method of treating timber; and the arguments for and against it are set forth with much ability and precision. While, on the one hand, it is fully admitted that the sap juices exert a powerful and deleterious influence upon wood, and that their removal is essentially produced by immersion; yet they observe

It is contended, on the other hand, that their expulsion may be produced by other and more advisable means; less sudden, but more salutary in their operation, and unattended with any of the ills arising from immersion; that a succession of wet and dry devests the fibres of the wood of their natural tenacity, adhesiveness, and organization, when exposed in the open air; the wet, swelling, and the dry separating, the soft fibres; that one of the tendencies of immersion is to render the wood porous, and subject it peculiarly to the action of the atmosphere; that in this porous state timber, confined as it must be when brought into use, where there cannot be a free circulation of air, and where a greater or less degree of humidity must prevail, the interstices become filled with putrid, corroding matter, and decay ensues; that timber exposed to intense frosts, after immersion, by which it becomes water soaked, or saturated with water, the pores of the wood become over distended, and in that state remaining fixed, the elastic adhesiveness of its fibres, and their power of contraction, are destroyed; that a firm, adhesive consolidated state of fibre is essential to great durability; that this state never can be produced after the timber shall have been saturated with water, and its pores once distended; that, if the timber be not cut while in a vegetative state, and be kept under shelter, exposed neither to rain, to the heat of the sun, nor to piercing winds, yet having a free circulation of dry air, nature will expel the sap juices, without the aid of any artificial

means.

It is further contended, that timber of close texture, such as live oak, or the best white oak, when once saturated with water, cannot be dispossessed of its moisture, in any reasonable time: that, when 'put into a ship, it imparts to the surrounding atmosphere a degree of

humidity which damages the provisions and stores, and generates diseases among the crew; that timber, in a dry state, is not subject to the destructive effects of frost, one of the most insinuating and irresistible of all, operating on the texture of bodies.'

The report then proceeds to state, that—

With respect to other materials of wood, the result of the experiments made many years since, would seem to indicate the inefficacy of covering as a means of preservation. The white oak and pine, collected under the act of 1799, and placed under sheds, was in a few years found in such a state of decay as to be unfit for use. The Commissioners know but little of the history of the oak and pine collected at that period. Whether the trees had attained their full growth-whether they were not cut in a vegetative state-whether, when stowed, the timber was properly stuck, so as to admit a free circulation of air-whether the sheds were of a sufficient width and height to protect it against the sun, or sufficiently tight to secure it against rains and piercing winds-whether the timber had not been water soaked, prior to its being placed under sheds, are points upon which the Commissioners possess no positive information. Since, however, universal experience affirms the inefficacy of this method of preserving ship timber, the Commissioners are persuaded that these causes of decay must have existed in a greater or less degree; and that the result of experiments so partial and unsatisfactory, should by no means deter us from adopting it as far as circumstances may render it expedient to do so.'

The insufficiency of immersion, or covering in the ordinary way, to preserve timber from rot, having thus been stated, the Commissioners then propose, as a substitute,

That the whole frame should be put together, and planked, bolted and stayed, so firmly that no piece could spring out of its place or shape, and covered so effectually as to be protected from the sun, moisture, and high piercing winds, yet to admit a free circulation of pure dry air.'

In favour of which mode of managing ship timber, they state, that

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. Many instances might be added of the great durability of ships thus built and preserved: one, if not more, occurred at Venice. ship built there remained on the stocks, under cover, for sixty years, when, on being examined, no mark of decay could be discovered in her timbers; they were somewhat shrunk, which was ascribed, no doubt justly, to their having been put in the ship in an unseasoned state. Escalier observes, we perceive that wood used on land, kept dry and under shelter, will preserve itself for ages." Thus preserved, the wood acquires a close texture, a hard consolidated fibre, which prevents its imbibing moisture, and enables it to resist all the destructive effects thence arising.'

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We readily acknowledge, that as far as they go, there is much

good sense and sound reasoning in the above extracts from the report but before entering fully upon the subject, we cannot omit to remark, that for every vessel thus built under cover, possessing superior qualities of durability, hundreds may be adduced in favour of such as are built in the open air; and it is questionable, as this system has been practised for some time past both in Europe and in this country, whether it does not furnish as many instances of premature decay, as of superior durability. The circumstance stated by Escalier, admits of no dispute; but its application, as well as that of the instance of the Venetian ship, only extends to vessels upon the stocks and in ordinary, since the moment they are at sea, new circumstances and combinations take place which must produce new consequences. From the best consideration which we have been able to give the subject, we cannot discover, that the plan proposed in this report amounts to any thing more in effect than an entire rejection of all the methods heretofore practised for the preservation of ship timber, except such as were in use centuries ago; and, in fact, notwithstanding the change of circumstances, it leaves us without any more knowledge than was possessed upon the subject in the time of Vitruvius. That a number of errors have existed in regard to the management of timber to prevent decay, and that a vast many of the schemes which have been proposed have proved visionary and chimerical, there cannot be a doubt; but it does appear to us that there are principles emanating from the present enlightened state of human knowledge, which, if properly applied, must be attended with salutary results; and until experience shall clearly prove them to be founded in error, it is the part of wisdom to attribute their want of efficacy rather to an imperfect application of them, than to any radical defects which they may possess in themselves.

In reasoning upon the causes of durability and of decay in ship timber-there are some facts, which, if properly appreciated, will, we think, assist us to form an opinion whether there be not some mode of preparation which shall prolong its existence. We know that live oak is more durable than hemlock and as the fibre of all wood is substantially composed of the same ingredients, and as it is known that neither of these possesses any peculiar oil or acid which can resist the effects of corrupting causes or can promote decay; it follows, therefore, that the strongly marked character of durability, in live oak or locust, is to be attributed entirely to the closeness of their textures, or, in other words, to their being more solid and compact than other timber. This being granted, it also follows that, to render live oak or locust as durable as possible, it should

be so managed that it shall acquire the greatest degree of compactness or solidity of which it is susceptible.

There is another point, to which the ingenuity of man has been more particularly directed,-viz: that as corruption is produced by the combined agency of heat, air, or moisture, if one or all of these be excluded by artificial means, the subject will be rendered more lasting:-thus wood, when immersed in water, will endure for centuries, because air is excluded;—when placed in dry houses, also, because moisture is excluded;-or, when kept in an atmosphere below thirty-two degrees of Fahrenheit, because that deleterious heat is excluded;-thus resisting the effects of the other two agents, which in each of those cases are left to exert their influence freely. Having thus stated the form in which we think this subject should be considered, and the particular points to which our inquiry ought to be directed, we will now offer a few remarks upon,

1st. The best mode of increasing the solidity of timber:

2d. The best method of seasoning ship timber, and of excluding from it, or preventing the deleterious effects of, either heat, air, or moisture, by artificial means.

And in the course of these remarks we shall take occasion to comment upon the usual mode of seasoning timber, the object of which is simply to expel the sap juices.

It appears to us that the experiments of Buffon are conclusive, in regard to the best mode of increasing the solidity of timber; which is to detach the bark from the tree, while standing, (this being the most readily effected in the spring, when the sap flows actively,) and sufferit to remain in that situation for one, two, three, or four years. Buffon found, from a number of experiments accurately made, that timber, thus treated, invariably possessed more strength and solidity than any that was differently treated; and particularly, he ascertained that the sap wood of a tree, deprived of its bark and left standing for four years, possessed more strength or solidity, than the heart of a tree felled and seasoned in the usual way. The rationale of this phenomenon apparently is, that the sap flows through the pores or vessels of the wood to the leaves-whence, after undergoing some preparation, it is transmitted between the bark and the wood, and there becoming indurated, it produces annual concentric layers or circles. These circles, or layers, possess different degrees of solidity, diminishing from the center to the circumference; the outer circle being always the most open and porous. The sap being thus transmitted through the cells or pores of these layers with different degrees of activity, increasing from the centre to the periphery-it follows that the

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interior layers of the wood are annually acquiring more and more solidity, by assimilating to themselves the sap in its ascent, and a portion of which is indurated. Thus the sap, which by the ordinary method of seasoning timber it is intended to expel, is in this manner, for a certain period, filling up the pores of the wood, until its functions completely cease.

There is an evil, to which timber is much exposed in the progress of seasoning, to wit, that of rifting or cracking, caused by the sudden contraction of the exterior surfaces of the wood which have first parted with their moisture. It will readily be perceived that, as the timber when used is placed upright, each of these cracks or rifts becomes a channel to convey water into the very body of the wood. This very serious inconvenience is only to be obviated, if at all, by a gradual and uniformly accelerated desiccation, which we think is in a great degree effected by this mode of drying timber; for as the functions continue gradually to diminish until the tree expires, the sap juices are withdrawn from the interior to the exterior of the tree, and either evaporated, or exhausted in the formation of buds.

The usual mode of treating timber appears to us to be very imperfect. The tree is cut down in the autumn, or beginning of winter, under the idea of its containing at that time less sap than at any other season of the year; it is then hewn and housed under sheds open all round to admit a free passage of the air: both of these procedings are founded in error. The pores of the wood contain nearly as much sap in the early part of winter, as at any other season of the year. For as the sap which produces the leaves and buds in the spring cannot have been transmitted from the roots that season; the supply must be derived from the cells of the wood, which are a kind of storehouse of sap to furnish a stimulus for the latent energies of the spring shoots, and which, from the physiology of vegetables, as well as the ordinary operations of nature, are first brought into action by the returning heat of summer. The roots are much later in being acted upon by this heat, and therefore do not acquire sap until some time after the buds of spring have put forth. It is reasonable therefore to infer, that the pores of the wood are most clear of moisture at some moment after the first budding and before the full development of the leaves, and that the tree should then be cut down. The cold, or frost of winter, is also an important agent in hardening the soft portion of wood formed in the previous summer; a circumstance which is not sufficiently estimated in the preparation of timber. We think, therefore, that the tree should be felled in