« PreviousContinue »
ed by the ends of the beams, so as, in time, to produce putridity. The other three sides are between decks, and at least so far dry as not to be exposed to actual positive wet; but existing, as they do, in a heated atmosphere, from the closeness and confined'space, are liable to be acted upon by an unwholesome and destructive caloric and effluvia, exactly calculated to promote the principles of putrefaction, for want of a sufficient quantity and circulation of fresh air to carry it off. By this the juices of the timber are, through the means of the fermentation thus excitert, put into motion ; and the timber is perpetually emitting and absorbing again, without any
correction of their noxious qualities, the principles of putridity, which it is the office of the fresh air, when it can be permitted to act freely, to absorb.
In these two comparative situations, the difference of temperature has been found, by actual experiment and computation, to be far greater than any one, who had not tried it, would be inclined to believe or imaginé. For those parts of the beams between the linings are placed in an atmosphere of about 40 degrees, while those between the decks are exposed from 60 to 80 degrees. This is exact-' ly the same difference of temperature as is required to produce ac- : tive vegetation in the growing tree, and which is the sole cause of the decay of tiniber in ships ; and whenever it has happened that a ship has been very soon destroyed, it has been that the inequality of the temperature of the atmosphere has been great, which is sufficiently evident from the circumstance of the different degrees of soundness or decay in the different beams, according as it has happened they have been more or less exposed to the influence of both heat and moisture.
Again, we see fir timber floated up and down the river, for a considerable distance, from one place to another, or suffered to lie soaking in the river for months together: three sides of the piece of timber are evidently exposed to positive wet in a very great degree, nay, even to saturation; and the fourth, being the upper side, is subject to no degree of damp or wet, except what it may occasionally, experience from the rains or dews, but has to sustain the effects of the air and sun: so that the three sides are positively wet, while the fourth is, in all respects, the reversé. No one can doubt that the atmosphere and temperature of the two situations are abundantly different; nor can any one imagine any other than that the disparity in its consequences must be equally great ; and that the timber must be very much affected by that cause in the different parts, in proportion to the greater or less degree of heat or moisture, to which it is liable or exposed. If timber is always kept in the same position, so that the very same parts, and no others, should be constantly exposed to either of the two degrees of temperature above mentioned, and VOL. XVI. Pam. .NO. XXXII.
to that only, while the rest of it was subjected, as above, to the influence of the other, (but it is, beyond all dispute, so situated in ships and buildings,) this irregularity of temperature must necessarily introduce putrefaction and decay; arid this is most certainly the cause of all decay and destruction in fir and all other sorts of timber.
No piece of timber, however solid and sound in its own nature and constitution, can, for a constancy, stand the existence in a difference of temperature at the same instant ; viz. one part wet and the other dry. Nor can it, for any considerable space of time, support the variation of being alternately wet and dry; and Sir. Christopher Wren has himself noticed, that Venice and Amsterdam, being both founded on wooden piles, immersed in water, would themselves fall, if the constancy of the situation of those piles, in the same element and temperature, did not prevent the timber from rotting.'
The Alhambra Palace in Spain, supposed to have been built 3000 years, and mostly of timber, is preserved by the constancy of the temperature, supposed to be prepared with some composition.?
The same principle of equality of temperature is no less necessary to be observed in the application of timber to any of the purposes of common life. And in no case is it more requisite, than in the erection of houses and other edifices, whether for the purposes of private or public utility. But even in these, it is not uncommonto see timber so placed, and in such an inequality of temperature, that it must inevitably be destroyed, as it invariably is, in a short
space time, by that species of decay well known by the appellation of the dry rot. For instance, what can be more to the prejudice of timber, or more hostile to the idea of its preservation or continuance in health and soundness, than using it in the manner in which it is perpetually employed for boarding kitchens and other rooms, on the ground floor, where three sides of the joists, and the lower face of the flooring, are bedded in earth so moist, as to amount almost to positive wet, while the upper side of the joists, and the upper face of the flooring, is perfectly dry, and exposed to the effects of heat, from a large fire perpetually burning. The consequence of this has invariably shown itself, from time to time, in the circumstance of joists and flooring, laid down sound, and becoming rotten in a few months. Instances can be produced of two entire new floorings, laid down in the very same kitchen, in such a situation,
* See his Letter to the Bishop of Rochester, inserted in Widmore's History of Westminster Abbey; and also in Wren's Parentalia.
? See Murphey's account of this Palace, published by Cadell and Davies.
in less than ten years, besides the necessity for a third at the end of that time; independently of partial repairs, from time to time, and removing decayed pieces as soon as they were discovered.
Even where it has not, as here, been injudiciously or improperly placed, in situations so calculated to promote its very destruction, that it would have been wonderful had it escaped ; it has been found impossible to prevent its occurring in practice in the use and application of timber to those very purposes, for which it was apparently and evidently intended. Beams of the greatest soundness and health, that could be selected with the greatest possible care and judgment, and some of them of great strength and magnitude, have, in a very short period after they had been introduced into the walls of dwelling-houses, manufactories, brewhouses, and other similar erections, been discovered, although not apparently exposed to heat or moisture, subject to the dry rot; because some secret external or accidental circumstance, which could not be accounted for at the time, had imperceptibly introduced heat and moistu united, and so caused fermentation, by setting in motion the internal juices of the timber. Nor has the utmost degree of sagacity or foresight, which could, as yet, be exerted, been sufficient or able to secure every edifice or erection, with certainty, from experiencing more or less, in a very short space of time, the decay and destruction of some of its timbers; or the owner, from the necessity, in some cases, of perhaps taking down and re-erecting the whole, for fear it should fall.
It is not, however, to be inferred, from thest, or any other circumstances, that this natural propensity in timber to putridity and decay is necessarily invincible; or that it may not be conquered and effectually subdued, by a proper application of fit and adequate methods, already perhaps in existence. Neither is it to be hastily concluded or imagined, that because all former attempts for the purpose have hitherto failed, all future endeavours must in like manner be equally destitute of success. On the contrary, the possibility and practicability of such a remedy is here intended to be established; and it is only owing to their being founded on false principles and erroneous ideas, that all other attempts have missed their aim The facts already stated, which cannot be controverted, have already decidedly shown, that no proposal for this object can succeed, which does not rest on the principle of excluding foul air by means of a pre-occupation of the pores, by the interposition of some medium in such a manner, as to prevent the possibility of its ever being admitted at any future period, by any circumstance whatever. And this can only be effected by saturating the timber with some such impenetrable composition, not to be soluble in water, or moveable in a temperature under 200; and if timber can be
made to resist that degree of temperature, there is no situation in which it can be placed that will effect it; and it must be sufficiently potent and efficacious to repel any attack from heat and moisture, and to prevent their union from operating in any manner on the timber; by which means it may be rendered capable of being employed without any injury in any situation, however unfavorable. Such a remedy has actually been found; what it undertakes to perform will be more succinctly stated in the ensuing section, and the evidence of its actual success will also be seen in subsequent pages, in an enumeration and particularisation of a series of experiments, made in every way in which it was jueged possible to try and ascertain its validity.
ON THE NATURE OF THE PROPOSED REMEDY, AND THE
SEVERAL OBJECTS TO WHICH IT IS APPLICABLE.
The general object of the remedy intended to be proposed, or suggested, which consists in the application of a liquid composition, is the very important and weighty purpose of rendering timber, after the application of the composition, impervious to moisture of any kind; and so effectually is this object attained, that the liquid introduced, by which the destructive matter is expelled, can never itself 'be dislodged; but it lies in the pores in a concrete state, and presents an invincible opposition to all other fluids.
By this introduction, the timber, as has been actually ascertained by experiment, is capable of being so increased in strength, that though a section of rotten oak branch, not prepared, was broken by the weight of 34 pounds; the other section of the same branch, prepared with the composition, could not be broken by the weight of 112 pounds; 207 pounds was afterwards tried without breaking the section.
Strength and durability being its general quality, and undoubtedly a very extensive object, it is almost superfluous to say, that it must be of the greatest utility possible in every branch or department in which timber, or wood of any kind, is employed; and as these are so various, it is impossible, and therefore hopeless to attempt it, to particularise or enumerate them all.
The power and effect of this composition is so great, that it cannot be evaporated, forced out, or extracted, either by damp or the heat of the sun, nor by any exposure or confinement.
Nor will the timber be liable to contract or expand, the pores being made completely impervious to moisture.
form of gas.
The additional strength given to timber is, by uniting and consoJidating the component parts of which it consists, even by making the sap of oak equal to the heart.
It will effectually prevent the dry rot; because the internal juices cannot be set in motion, as heat and moisture, the parents of fermentation, cannot find admission.
And as, after the application, the timber becomes impervious to wet and moisture, it is evident that no fungus can be generated; nor the high state of fermentation be created to destroy it in the
The increase in the strength of timber, after the application of the composition, has been found by experiment so great, that a beam of fourteen inches square will be rendered equal in strength to one of sixteen; and one of ten and a half inches to another of twelve, &c.
The reduction of scantling, which it is obvious may be made in consequence of the above fact, and which may equally take place in all cases, without exception, in which timber is used, would, in itself, be, in a very short time, an immense saving of expense and timber, with the additional circumstance of an increased durability; and the advantages, to state it only in one instance, would be, that a ship might be constructed many tons lighter with equal strength, and the cargo will be securely protected from damp and mildew.
In the red and yellow pine, the increase of strength has, on experiment, been found equivalent to one sixth; so that scantling, one sixth less, would be equally strong, and might be used with safety. And it is certain the yellow pine, prepared with this composition, is equal to red, or at least to red not so prepared; or, to express it perhaps more intelligibly, to the present strength of that species, so as to make inferior yellow equal to the finest red.
The size of masts and spars might be much reduced in consequence, and upon the principle of the additional strength they would receive from this composition.
Boats and barges would be rendered much more secure from leaking, &c. by the use of this composition, as well as stronger, and not so likely to be staved, &c.
This composition acts also very powerfully upon iron; for, if prepared, it may be exposed in the rain for years without contracting the least rust.
All the timber and iron used in the Ordnance department would also be greatly improved by this composition, not only in resisting the effects of wet and dry, heat and cold, but also in the reduction of scantling, and the increased durability both of wood and iron; consisting of every material used in artillery, fortifications,