249 



TIMBER AND TIMBER-TRADE. 



TIMBER AND TIMBER-TRADE. 



250 



their wood does not permit of being worked into many shapes ; but 

 its cylindrical form affords great facility for constructing a variety of 

 utensils, and for application to the simple wants of man in tropical 

 climates. The stems of Exogens are solid, and the older the tree 

 becomes the more solid is the wood. Hence a distinction is made 

 between the centre of the wood of the trunk and its circumference, 

 the one being called heart-wood, the other sap-wood. The heart-wood 

 is the seat of the deposition of the peculiar secretion of the tree, and is 

 frequently separated from the sap-wood by a distinct line. It is the 

 eccretioji in the heart-wood that renders it darker, harder, and more 

 durable than the sap-wood ; and for practical purposes it is of import- 

 ance to distinguish between the one and the other. There is much differ- 

 ence between the relative sizes of the ultimate woody fibres of which 

 wood is composed ; and the durability and tenacity of wood frequently 

 depend on the fineness of its fibres. It is to the secretions deposited 

 in the wood, probably more than to the fibres themselves, that wood is 

 indebted for its varying degrees of density. Thus, although it has 

 been ascertained that woody fibre itself has a specific gravity of about 

 1-50, water being 1, yet there are many woods whose specific gravity is 

 lighter than water on account of the mode in which their fibres are 

 arranged. The conducting power of wood in relation to heat is a 

 matter of importance in the construction of buildings and other pur- 

 poses. In some experiments performed by Delarive and De Candolle 

 on prisms of different kinds of wood, to ascertain then- power of con- 

 ducting heat, they found that the direction of the fibres materially 

 interfered with their conducting power. Thus it appeared that the 

 obstruction to the passage of caloric was greater when the current was 

 at right angles to the woody fibre than when it flowed longitudinally 

 in the direction of the fibres. This difference also appeared to increase 

 in proportion as the wood was a bad conductor of heat. The cooling 

 power of these woods is another important point, and this is not at all 

 in relation to their conducting power : thus fir-wood being 100, the 

 cooling power of oak-wood is only 30-38, whilst that of beech-wood is 

 120-2; whereas, in conducting power, if fir-wood be taken at 100, then 

 beech-wood is 83'19, and oak-wood 134'10. Another important point 

 of inquiry with regard to the physical properties of wood, as to its 

 value in building, &c., is its relation to moisture. The less the specific 

 gravity of the wood the greater is its capacity for moisture : fir absorbs 

 more and teak less than most other kinds of timber. 



It is the peculiar resinous, gummy, oily, or other secretions, that 

 give to the various woods their different colour, smell, and taste. The 

 colouring matter is sometimes deposited in such abundance as to 

 render it useful for dyeing, as seen in log-wood, red sanders-wood, and 

 other woods used as dyes. Some woods have volatile oils deposited in 

 them, which, being slowly given out, render them odoriferous ; and 

 this is the case with sandal-wood, rose-wood, the wood of cedar, fir, and 

 other trees. Frequently bitter and other secretions are deposited in 

 wood, giving it a peculiar taste, and rendering it useful in medicine. 

 The wood of the quassia, as well an of the sassafras, are examples of 

 this kind of use. The wood of trees frequently contains in small 

 quantities the secretions which are deposited in other parts of the 

 plant. 



If wood be submitted to destructive distillation, it is decomposed, 

 and the consequence is the production of acetic acid and an oil, which 

 pass off, leaving a certain quantity of charcoal. Taking them one 

 with another, the chief kinds of English timber yield, by the distilla- 

 tion of 1 Ib. weight, about 7i ozs. of wood acid, 3J ozs. of charcoal, 

 and 1J ozs. of oil. 



The woods that are used by the cabinet-maker for furniture of a 

 more delicate kind are called fancy-woods. The use of these has 

 become much more general since the introduction of the art of 

 veneering ; and now that this is done by machinery, instead of by hand, 

 many woods are xised for furniture and other purposes which, on 

 account of their scarcity, could have been formerly used only to a 

 very limited extent. The most common of the fancy woods, and that 

 which is used most by the cabinet-maker, is mahogany. Next in point 

 of importance and use to mahogany is rote-wood. Xing-wood is a 

 beautiful wood, used only for delicate articles. Beef-wood is a very 

 heavy wood, of a pale red colour, and is brought from Australia in logs 

 9 feet long and 13 or 14 inches wide. Tulip-wood is brought into the 

 market in very small pieces, not more than 4 feet long and 5 inches in 

 diameter. It is clouded with red and yellow colours, and is used 

 for bordering and making small articles, such as caddies and work- 

 boxes. Zibra-icood is the production of a large tree, and is cheap 

 enough to be made into tables, piano-fortes, &c. It is coloured brown 

 on a white ground, and clouded with black. Salin-icood is of a brilliant 

 colour, with delicate glowing shades. It is found in the market 

 in logs 2 feet wide and 7 or 8 feet long. Sandal-mood is of a light 

 brown colour, with golden-coloured waves. Ebony and iron-wood arc 

 the names given to some very hard woods, mostly brought from India, 

 although some of the species are found in Europe and America. 

 Canary-trortd hag a deep yellow colour. Pwple-v>owl has a purple 

 colour, without veins. Snake-wood is of a deep red colour, with black 

 shades. Calamander-wond is a handsome cheap wood, taking a high 

 polish, and is brought from Ceylon. Other woods are called from the 

 places they come from, as Coromandd wood, Amboyna wood, &c. 



The practice of staining wood is sometimes had recourse to for the 

 purpose of making the more common woods resemble in colour the 



fancy-woods. A method has been proposed of doing this by introducing 

 into the tree during its growth various colouring agents, so that during 

 the course of the ascent of the sap the colouring matter may be taken 

 up and deposited in the woody tissue. Some of the woods thus treated 

 have been made to assume very remarkable colours ; but as the trees 

 on which it can be practised are too soft ar.J eoarseyior fine work, it is 

 not likely that this method will at all supersede the use of the naturally 

 beautiful fancy-woods. 



Growing trees are exposed to the attacks of animals and of insects, 

 in addition to their own natural causes of decay ; and when they are 

 used as timber they are still liable to the attacks of insects and of 

 worms of a peculiar description. The mischief done by animals is of 

 a comparatively simple and limited description; and may briefly be 

 described as consisting in blows and wounds of the trunk, and in tlje 

 violent disruption of the smaller boughs, thus rendering the formation 

 of knots more frequent than might otherwise be the case. Birds are 

 actually of service in woods, for the carnivorous birds do good by keep- 

 ing down insect life. The woodpecker and nuthatch only attack the bark 

 of trees when in search of the larvse boring in them ; rooks and crows 

 destroy immense numbers of the larger beetles ; and, in fact, nearly all 

 the forest-feeding birds render the same service. Squirrels, bats, and 

 other insectrdevouring mammalia, play the same part in the economy 

 of nature ; so that our attention may almost exclusively be devoted to 

 the consideration of the attacks of insects and of the boring worms. 



There are three descriptions of insects which prey upon trees, 

 which may be classified according to the parts they especially attack, 

 namely, those which attack the leaves, those which attack the bark and 

 the alburnum, and those which attack the heart-wood. The leaf-eaters 

 are of countless varieties, some of them eating the upper, some the 

 under surfaces, and others the substance of the leaves without touching 

 the epidermis. Again, there are insects which only attack the flowers, 

 some living upon the farina of the flowers, others on the fluids in 

 the vessels of the flowers, and others on then: leaves ; whilst there are 

 also other insects which injuriously affect growing timber by giving 

 rise to galls or other analogous excrescences. The principal mischief 

 caused by this description of insects consists in the interferences they 

 produce in the flow of the sap, and in then- interferences with the 

 respiratory functions of the leaves ; but fortunately their ravages are 

 apparent, and their enemies are extremely numerous, both in the ani- 

 mal and the insect tribes. There are several varieties of the bark- 

 feeders ; some of them attacking exclusively the outer bark, some the 

 inner bark, and- some the alburnum. Then- ravages, however, in all 

 cases are exercised only superficially, so to speak, and they do not affect 

 the quality of the timber in any serious manner. These insects may 

 kill a tree, but the heart-wood will remain sound, whatever be their 

 numbers. Such insects as the Scolytui dettructor will, nevertheless, do 

 more injury to a forest in a month than all the animals it may shade 

 could do in a decade. The Hyletim.uifra.rini, the Tomicus typoyraphi- 

 ciu, the Sotrichu pinattri, the Sphinx apiformis, the Curculio abreitis, 

 and the Curculio notatut are almost equally mischievous ; whilst the 

 Lymexylon attacks both the alburnum and the heart-wood. Of the 

 heart-wood devourers the most dangerous in our latitudes are the 

 Count liyniperda, the Cryptorhynchut lapathi, the Lucanidce, the Ceram- 

 bycida, the Sirex giyas, the Sirex duplex, and the Zengera etculens ; and 

 of these, the Coaui and Sirex of our own latitudes, and the Prionui 

 giganleui and the Callidium giganteum of tropical climates, together 

 with the Lymej~ylon, attack the converted timber after it has been long 

 removed from the forest. 



Of the boring-worms the only varieties hitherto specially noticed 

 are the Teredo navalii and the Limnoria terebrans ; and their ravages 

 seem to be the most dangerous when wood is exposed to them in 

 decidedly salt water. The Limnoria, however, occasionally attacks 

 timber in slightly brackish water, and it would seem that both these 

 species of worms have an antipathy to water containing sulphuretted 

 hydrogen, or some of the vegetable and mineral acids ; for they do not 

 attack timber driven into the sea-shore near the outlets of sewers, and 

 they avoid timber which either contains, naturally, considerable pro- 

 portions of pyroligneous acid, or has been artificially impregnated with 

 creosote, sublimate of mercury, sulphate of copper, &c. The supposed 

 immunity of the green-heart timber was long attributed to the exist- 

 ence of some such quality in it ; and though it is now known that the 

 boring-worms do attack that wood, they certainly do not destroy it 

 with anything like the same rapidity that they destroy fir, beech, elm, 

 or even oak. Notwithstanding the fearful nature of the ravages caused 

 by the boriug-worms, the habits of those creatures have not been tho- 

 roughly studied ; and it is difficult to trace the conditions which tend 

 the most decidedly to their multiplication. It would seem, however, 

 that both the species are to be found in the greatest numbers in warm 

 latitudes ; that the Teredo prefers the sea-shores from which it can 

 derive the carbonate of lime necessary for its growth ; that the Lin- 

 nrtria, on the contrary, prefers the shores upon which the sands arc 

 charged with the decomposition of silicious rocks ; and that the por- 

 tions of the timber devoured by both these worms occur a little below 

 and a little above the lines of high and low water : these worms, in fact, 

 require both air and water. The works of Messrs. Forbes and Hanley 

 (' History of British Molluaca '), Cailliaud (' Mdmoiro sur les Mollusques 

 perforantes '), ' L'Instructiou sur les bois de Marine," published by the 

 French Government, and a Keport by a Commission of Dutch engineers 



