stopped, the tree dies: if the latter is set in motion by fermentation, the timber rots.

Heat and moisture, when in unison, never fail to produce fermentation in the juices of timber; and the property of fermentation is to expand, distend, and dilate the tree, when growing, and to cause corruption and putrefaction, after it is cut down. In both cases it is the same principle, motion by fermentation, which occasions the effect; and that only by the same means and method, the motion or agitation of the juices.

Matter and motion are still further exemplified, in the case of the vegetable kingdom, by the circumstance that, in all its productions, from the tenderest flower upwards to the sturdy oak, they are propagated by portions of matter comparatively very small; such as merely a seed, or a slip, or cutting, which, if not sown or planted, would remain at rest; but, when sown or planted, the power of vegetation sets their juices in motion; and this motion, however small in degree, will not stop or cease, without some cause to impede it. Frost, and the chill of winter, will, for a time, check vegetation, till the sun has acquired sufficient power to set it again in motion and thus it is, by the power of setting vegetation in motion in the juices, that the tree grows and expands; and, from a mere shoot or acorn, in the case of the oak, becomes, in the of about two centuries, a stupendous and magnificent tree.

space

While the juices of the tree proceed in their natural direction, and the same proportions of heat and moisture, as settled by nature, are preserved, which, of course, they in general are, so long as the tree is standing and growing, the effect is visible in the consequent health, improvement, and increase of bulk, and also in the production of the external foliage peculiar to its kind or species: but, if the course of its circulation be impeded or checked, or the quantities and proportions of these principles of heat and moisture be varied, as they sometimes are, by the intervention of some accident, when growing, and, more usually, after it is cut down, the consequence is seen in a deviation from the usual mode, by decay, sometimes by the production of fungi, a species of spungy excrescence or protuberance, affording a certain sign of the approach of internal putridity : for, in this last case especially, the tree, when cut down, does not lose the principles of vegetation, but they remain, perhaps, for a time, inactive, though certainly capable of being set in motion, till at length they are forced into action by a change of temperature, or the exposure to different elements: and this naturally leads to the consideration of the point as to equality of temperature, and the effect produced when that is not the case; from which it will be decidedly shown, that the premature decay of timber is occasioned by its own internal acetous matter in fermentation; and its decomposition or

destruction effected, by the circumstance of the concrete juices being forced again into motion by some accident, or by some change, which has taken place in the relative proportions of heat and moisture, which will be explained in the next section.

The construction of timber is not sufficiently studied, so as to account for the longer durability of some ships to others; and more particularly to those which have been noticed for their length of service, viz. the Royal Sovereign, Royal William, &c. The above two ships were built by royal order: the timber was particularly selected from an immense stock, of which at that time England could boast. It is evident, from the following extract, very large timber was selected, which will lead to, and prove the point, which I wish to estalish, that the centre of the tree is the most prone to decay, although no appearance, of decay is visible when the tree is cut down.

Extract. In "a description of his Majesty's ship Royal Sovereign, built at Woolwich in the year 1637, to the glory of our English nation, and not to be parallelled in the whole Christian world, one thing is particularly worthy of remark at least, if not of admiration (her timbers); one oak tree made four of the principal beams of this great ship."-"In the year 1684, which is 47 years after she was built, her planks were stripped off, and the original timbers that were then remaining in her were sound, and no easy matter to drive a nail."

The centre of all vegetables is the tenderest part: and in the very centre of a tree lies the circle of propagation; which, if possible, should always be cut out, as it is the first part to decay, after the sap. A beam made of one whole tree, may be stronger than one of the same size cut out of large timber; but if a tree is large enough to have one or two saw-cuts down the centre, the circle of propagation is cut out, or laid open to season, therefore beams and other scantling cut out of large timber are not so liable to decay; which I conceive is proved in the case of the Royal Sovereign, and no doubt was the case with the Royal William, &c. Hill, on the construction of timber, is very elaborate on this subject. He proves that all new shoots protrude from the very centre of the branch, and that in the very centre of the trunk and the branches, the same component parts of the tree lie in embryo; that is, in the very centre is a circle, consisting of rind, bark, sap, and heart, ready to protrude whenever nature calls them forth: this circle is what has often been erroneously taken for the pith; and when the tree has arrived at maturity, it is the first part to become rotten: hence, hollow trees, and the cause of beams and girders being often rotten, when the smaller scantlings are sound: this circle contains more acid in proportion, consequently more subject to fermentation.

It is proved by Mr. Goetling, in Crell's Chemical Journal, 1779,

that all timber contains, more or less, the same kind of acid, which is chiefly composed of hydrogen and charcoal.

There can be no doubt, but it is the acid that causes fermentation in timber, when placed in a situation favorable to create it-which it is the property of my process to prevent.

My opinions upon the cause and effect of premature decay, and the various causes of decomposition in timber, may appear new, particularly to those who have fallen in with the old opinion; still, should the opinions of others be considered more consistent, as to the origin of the disease, my remedy to effect the preservation of timber is the same: I have only to observe, my experiments bear me out, and support my opinions; and that my rules are grounded, according to Sir Isaac Newton's lesson," by just inductions from experiments and observations, to discover the laws of nature, and then to apply those laws to the solution of the phænomena in question."

SECTION III.

ON THE CONSEQUENCES OF EXPOSURE, IN THE CASE OF TIMBER, TO INEQUALITY OF TEMPERATURE OR ATMOSPHERE.

A TREE, while growing, is, at all seasons of the year, exposed to two different degrees of temperature at the very same instant; for the part above the ground is subjected to one degree of atmosphere, while the roots, and that below it, are as certainly placed in another. In winter the roots are in the warmest, and the upper part in the coolest temperature or situation; and frost and cold, by checking, in the upper part, the necessary heat, put a temporary cessation to the progress of vegetation, so as to reduce it almost to rest. The utmost, therefore, which the roots can do, secured, as they are, from the inclemencies of the weather and the severities of frost, by being buried in the ground, is to preserve, in nearly a state of comparative inactivity, a supply of those principles of heat and moisture, in their necessary proportions, which may afterwards be set in motion, when the return of summer and genial warmth shall restore to the upper part of the tree the activity of vegetation. If it were not thus, the tree must die, for want of the necessary materials to sustain it; and it is the absence of this supply, and that renovation from the earth, of which the tree is deprived, when it is cut down, and consequently severed from the earth, its parent, that prevents a tree, when cut down, from vegetating as when standing. The reason, therefore, why the vegetation of the tree is checked in the winter, is this, that by the

wet the moisture is increased, and by the cold the heat abated; so that the proportion of the former is rendered greater, and that of the latter less, by which means the relative proportion, established by nature, as necessary for the progress of the growth of the tree, becomes destroyed.

In the summer, the situations are exactly reversed; for then the roots are in the coolest station, as being protected from the heat of the sun, and the upper parts of the tree are in the warmest, as being exposed to its rays. And as this tends to relax the rigidity and stiffness of the fibres of the tree, and to counteract the effect of the cold in the upper parts, by opening those pores which the cold had closed, and expelling that moisture with which they had been filled, the proportion of moisture, which the tree had acquired in the winter, becomes lessened, and the heat increased; so as to restore the necessary vegetative power. Vegetation is, therefore, then active, and the operations of nature are exerted in full force.

It is evident, that, in this process, the juices enter the roots in a cool and unfermented state; and are permitted to ascend, according to their nature and aptitude for that purpose, through capillary tubes, to the top of the tree and the extremities of its branches, which they cannot effect in winter, because the stiffness and want of elasticity in the fibres, occasioned by the operation of the cold, produce a degree of resistance to the ascent of the fluid of the juices, which that fluid is unable to overpower. But, in summer, the warmth of the sun opens the pores of the upper part of the tree, relaxes its fibres, and removes that impediment to the ascent of the juices by which they had before been checked. The juices of the tree, in their passage to its summit, and to the extremity of its branches, naturally acquire the principles and nature of the tree, so as to give them a tendency and propensity to produce one kind of foliage, in preference to another; and, as what is thus communicated from each tree must, of course, bear a relation to its own species rather than to any other, the juices, thus impregnated, become capable of producing that kind of foliage peculiar to the species of tree through which they have passed.

As motion is the cause of friction, and friction produces heat, which may, in the instance of solid bodies, be so increased as to burst out into a flame, so fermentation is, in the case of vegetable productions, the consequence of heat and moisture united and confined; and hence must arise, from the over action and exertion of the parts, a degree of heat which would infallibly tend to putrefaction, were it not, that the juices, which, when acted upon, emit their superfluous heat by exhalation and perspiration, and receive and admit in exchange, through the valves, which operate as pumps, a

sufficient portion of cool and fresh air to counteract any such effect. Fermentation is, therefore, the principle of action in the juices, and the cause of vegetation; and, when thus corrected by the immission of fresh air, the health of the tree is preserved. During this active state of vegetation, the tree is under the influence of a high and low temperature: the roots are about 40, and the branches, &c. from 60 to 80; and, according to the different degrees of temperature, so is the slow or vigorous motion in vegetation created.

Similar causes must always be attended with similar consequences, so long as the bodies, to be acted upon, continue to possess the same qualities. And it is certainly true, that between a tree standing and growing, and one felled and cut down, there can be no essential change or difference of the principles and elements of which it is composed. In both cases it is capable of being acted upon by heat and moisture, though it no longer retains, when cut down, as in the instance of the tree when standing, the power or faculty of expelling, by exhalation or perspiration, the superfluous heat occasioned by the over action of fermentation. Unless, therefore, that power can be set at rest, and the effect of heat and moisture be in themselves destroyed, or some counteracting medium be interposed, so as to prevent the operation of heat and moisture on the timber, it is evident that the internal fermentation, unchecked, must be perpetually, though silently, undermining its health and soundness; and most certainly, though progressively, effecting its gradual destruction. The tree, therefore, whether felled in spring or in autumn, consists of exactly the same component parts or elements, and is full of the same juices, which, although suspended in their operation by the stop put to its vegetation, in consequence of its being cut down, are yet liable to be revived and called again into action, whenever any other cause than vegetation shall be found sufficient to give rise to that same degree of fermentation which that had formerly produced. And this, in the case of timber cut down, may be effected by local situation and an exposure to heat and moisture, either at the same time, or in uncertain and various succession; to which, on numerous occasions, it is frequently found: to be subjected.

In the case of a ship, the ends of the beams are situated between the inside linings and the outside planks; the top surface is covered by the floor of the deck, and both the ends and top surface are thus subject to much damp vapor and moisture. For, besides the portion of damp occasioned by the quantities of water with which the decks are perpetually sluiced, for the purpose of a due attention to the indispensably necessary objects of health and cleanliness, the space between the inside linings and outer planks acts as a gas pit, from which the noxious vapor from the hold ascends, and this is absorb