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THE MAGAZINE

OF

HORTICULTURE.

SEPTEMBER, 1847,

ORIGINAL COMMUNICATIONS.

Art. I. On the Importance of the Cultivation of the Oak and

other valuable Timber Trees; with Observations on the Preservation of Ship Timber, and the Process of Decay in Wood. By A. Mitchell, M. D., Portland. In a Letter to the Hon. H. A. S. DEARBORN. Communicated by Gen. Dearborn.

MY DEAR SIR, -The following article was communicated by me to Gen. Joseph M. Hernandez, of St. Augustine, Fl., and published in the Florida Herald. You will probably recollect that this 'gentleman has been, for many years, exclusively devoted to the science of Agriculture, and is one of the best systematic planters in that State. An Essay written by him on the Culture of the Tobacco Plant has been considered to be one of the most elaborate articles ever published on that subject.

Reasoning from analogy on the soil and productions of the southern portion of our Union, we may attribute to Florida, as having within its domains as many natural advantages as any of the tropical regions in the cultivation of those plants that are indigenous to those countries, presenting an extensive surface, which as yet remains imperfectly explored-rich in the spontaneous growth of many esculent plants for the support of man, and the growth of domestic animals, and offering a wide field for the cultivation and introduction of many more for exportation and home consumption. Such are the tea-plant, coffee, tobacco, sugar cane, Turkish poppy, olivetree, cotton, indigo, saffron, grape, fig, &c. As we shall VOL. XIII. NO. IX.

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briefly descant, at present, on the vital importance of a community being well versed in agricultural science, in order to improve with advantage those rich fields which a bounteous Creator has spread out before us, we shall principally advert to the forest-growth of this peninsular portion of our United States, with some original observations on the preservation of ship timber, and the process of decay in these woods.

As our navy may be considered the present and future bulwark of our safety as a commercial nation, it is not thought inappropriate to make a few remarks on those woods which are principally used in the construction of our ships of war and commerce.

The process of decay termed dry rot has been a theme of scientific inquiries for many years among many of our most eminent chemists; and the most elaborate investigations have been made, both at home and abroad, in order to ascertain the chemical effects of air, heat, light, and moisture, on the same, as our oaks and various timbers that have been previously prepared and appropriated to use for ship-building. We do not, at present, have the presumption to offer any preservative means that would counteract the effects of this dreaded enemy to our national purse, but simply to throw out some hints that may, in the future, be useful as a rallying point to others that can claim a precedence over their more humble brothers in the profession of science. The modern use of iron in the construction of marine vessels has been thought, at a subsequent period, would supersede that of wood; we should then have oxides to contend with instead of fungi; but we do not believe the former will ever supersede that of the latter. As the grand engine of navigation is deteriorating every day from the causes of decay, it may be asked, what is the dry rot? and how long has it been known to affect the timbers of vessels, and the cause of this effect? Well, in answer to the former, the dry rot is caused by the spontaneous decomposition of the vegetable albumen which acts as a ferment on the other constituent principles that may be present in the wood, as sugar and starch, which disintegrates the fibres of the wood, and accelerates the growth of mushrooms by the formation of ammoniacal salts. Of these fungi, there are two species, -as the Xylostroma giganteum, which grows in the timber like a thin broad patch of yellow leather, and the Serpula distruens, which is not so large, of a reddish color, and white at the edge growing externally. As the cause of this dry rot proceeds from an excess of vegetable albumen in those woods that have been in modern use for ship-building, we may answer the latter question by saying that the primitive oaks of Great Britain, and those of our country, which were used in the early construction of their navies, were not so rich in albuminous matter as the oaks of secondary growths, and those of various locations, are now; therefore the dry rot and fungous growths in such timbers were not known, nor never would have been, had we the timber now of those primitive forests of our country, Europe, and Great Britain. It will appear, by these observations, that we intend to maintain that the cause of dry rot proceeds from the negligence and want of knowledge in the selection of those trees which resist the effects of time and exposure without the process of decay. Such is our position, and, without further comment, we proceed to illustrate many points connected with the subject under consideration, as it is one of the most important to which the attention of a maritime people can be turned.

The oaks of North America, as described by Andrew Michaux, consist of twenty-nine species and varieties, most of which are useful in ship-building; the one considered the most useful, and stands at the head of the list, is the live oak, Quércus virens. It is a perennial tree, of slow growth, like the rest of its congeners, and is common to Florida, where the most extensive forests of this tree are seen. It is generally found growing from latitude 370 to Florida, “and westward to the mouth of the Sabine River," but never more than 15 or 20 miles from the sea. This valuable tree can be said to contain less of the causes of decomposition, as albumen, sugar, and starch, than any of the species hitherto described; therefore, it is the most durable, and less liable to decay; and, with all this natural immunity against spontaneous decomposition, we should not overlook the locality of its growth, age, and season of cutting for ship-timber. This is a necessary precaution, which is applicable to the whole tribe of oaks that are used in the mechanics. The best localities for the selection of durable timber from those trees, are elevated regions, high table lands, and an open country, where they are not overshadowed by other growths. They should stand where there is ample room for their branches, with a free access of air, heat, and light on all sides, as often seen on the boundary of some plantation, or as ornaments which venerate the mansion of the planter, or such like places. The woody fibres of such trees are more dense; they contain more carbon or astringent qualities, with less vegetable albumen : whereas, to the contrary of this, should such timber be cut in low wet grounds, ravines and shady places where they grow compact, it would be liable to decay from the causes mentioned, as there would be an excess of those constituent principles, and a softer structure that would hasten the decay, and cause the dry rot, so deleterious to our navies. The age of the oaks is next to be considered. They generally attain their maximum height and full development at the age of fifty or sixty years, and, aster that period, they progress but slowly, until they arrive at a very advanced age, as two or three hundred years or more. Those of the live oak that can be best recommended for durable timber, are such as have arrived to the period of a hundred years or more, if the constitutions of the trees are sound, and no visible decay is present. The gigantic growth of this tree at the age last mentioned far surpasses any of its species. The measurement of one of its limbs by myself in a horizontal line exceeded sixtyfive feet, while the diameter at the junction exceeded the size of the bodies of many red and black oak species of a full size, or secondary growths that have survived seventy winters. We repeat that the maturity of the species of oaks must be considered before used or appropriated for ship-building; for it is at this period the strength and durability of the wood are fully developed, and the longitudinal fibres tough and resisting. As the albuminous matter of which we have spoken is a nitrogenized compound, it is of a putrescible nature, and therefore forms food for insects, which penetrate the wood in various directions, admitting air and water to the interior of the timber. It is evident that this chemical action, or fermentative process, must be greatly favored by external causes, or the location in which the wood is placed. The close ap

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position and dense mass of timbers that are seen in the hull of a battle-ship of the line on the stocks is considered as favor-able to this action, although there are no doubts but what the germs of the disease are lurking in the timbers previous to their use, occasioned by the want of care and suitable selec. tion of appropriate trees, and preservation of the timber after cutting. The local sites of navy yards, where there must be a proper depth of water, unavoidably place the timber in a topographical situation that is unfavorable to the preservation of the wood, as heat and moisture accelerate the chemical action, and promote the fungous growths, whose nutrition depends on the chemical changes heretofore mentioned.

Could we always find a suitable hydrographical station for a navy yard, where, combined with its facilities, there was a dryness and purity of atmosphere, many of the causes that decompose the materials for ship-building would be prevented; but, as such localities cannot always be found in the surveys for such stations, we must patiently submit to the in.. jurious effects of heat and damp atmosphere, however well guarded the ships may be in their sheltered positions by ventilation and suitable protection ; although it is of the highest importance that the geographical situations of such places should be well understood and taken into consideration, as rivers, marshes, bogs, mean standard of the thermometer, barometer, and hygrometer, and mean quantity of rain.

The proper season for cutting such timber will next be considered. The months of July and August, when the trees are in foliage, and the juices circulating freely, is decidedly the best period for cutting; as then the greater portion of the albumen is contained in the cambium or descending sap, while most of the nitrogen is set free by exhalation, and is principally combined with the fluids that circulate exteriorly. The trees, after they are fallen, should be immediately rough hewn, and deprived of their sap-wood and bark, placing the timber in the most favorable situation for seasoning and desiccation by elevating it from the earth. The ordinary process of seasoning wood consists in merely exposing it to a current of air. It would be a desirable thing if we could find a location where

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