1730. The preservation of timber, the prevention of decay, and the causes of decay, will require from us a succinct notice; and we shall commence by placing before the reader the observations on the subject from the celebrated and venerated Evelyn, though perhaps at the risk of repetition in what follows. As King Henry V. is made by Shakspeare to say of Fluellen, "Though it appear a little out of fashion, there is much care in this" author. 1731. “ Lay up your timbers very dry, in an airy place, yet out of the wind or sun, and not standing very upright, but lying along, one piece upon another, interposing some short blocks between them, to preserve them from a certain mouldiness which they usually contract while they sweat, and which frequently produces a kind of fungus, especially if there be any sappy parts remaining.

1732. "Some there are yet who keep their timber as moist as they can by submerging it in water, where they let it imbibe, to hinder the cleaving; and this is good in fir, both for the better stripping and seasoning; yea, not only in fir, but other timber. Lay, therefore, your boards a fortnight in the water (if running the better, as at some mill-pond head); and there, setting them upright in the sun and wind, so as it may freely pass through them (especially during the heats of summer, which is the time of finishing buildings), turn them daily; and thus treated, even newly sawn boards will floor far better than many years' dry seasoning, as they call it. But, to prevent all possible accidents, when you lay your floors, let the joints be shot, fitted, and tacked down only for the first year, nailing them for good and all the next; and by this means they will lie staunch, close, and without shrinking in the least, as if they were all one piece. And upon this occasion I am to add an observation, which may prove of no small use to builders, that if one take up deal boards that may have lain in the floor a hundred years, and shoot them [plane their edges] again, they will certainly shrink (toties quoties) without the former method. Amongst wheelwrights the water seasoning is of especial regard, and in such esteem amongst some, that I am assured the Venetians, for their provision in the arsenal, lay their oak some years in water before they employ it. Indeed, the Turks not only fell at all times of the year, without any regard to the season, but employ their timber green and unseasoned; so that though they have excellent oak, it decays in a short time, by this only neglect.

1733. " Elm felled ever so green, for sudden use, if plunged four or five days in water (especially salt water), obtains an admirable seasoning, and may immediately be used. I the oftener insist on this water seasoning, not only as a remedy against the worm, but for its efficacy against warping and distortions of timber, whether used within or exposed to the air. Some, again, commend burying in the earth; others in wheat; and there be seasonings of the fire, as for the scorching and hardening of piles, which are to stand either in the water or in the earth.

1735. 66

1734. " When wood is charred it becomes incorruptible; for which reason, when we wish to preserve piles from decay, they should be charred on their outside. Oak posts used in enclosures always decay about two inches above and below the surface. Charring that part would probably add several years to the duration of the wood, for that to most timber it contributes its duration. Thus do all the elements contribute to the art of seasoning. Timber which is cleft is nothing so obnoxious to reft and cleave as what is hewn; nor that which is squared as what is round: and therefore, where use is to be made of huge and massy columns, let them be bored through from end to end. It is an excellent preservative from splitting, and not unphilosophical; though to cure the accident painter's putty is recommended; also the rubbing them over with a wax cloth is good; or before it be converted the smearing the timber over with cow-dung, which prevents the effects both of sun and air upon it, if of necessity it must lie exposed. But, besides the former remedies, I find this for the closing of the chops and clefts of green timber, to anoint and supple it with the fat of powdered beef broth [we do not quite agree with our author here], with which it must be well soaked, and the chasms filled with sponges dipped into it. This to be twice done over..

1736. "We spake before of squaring; and I would now recommend the quartering of such trees as will allow useful and competent scantlings to be of much more durableness and effect for strength, than where (as custom is and for want of observation) whole beams and timbers are applied in ships or houses, with slab and all about them, upon false suppositions of strength beyond these quarters.

1737. "Timber that you have occasion to lay in mortar, or which is in any part contiguous to lime, as doors, window cases, groundsils, and the extremities of beams, &c., have sometimes been capped with molten pitch, as a marvellous preserver of it from the burning and destructive effects of the lime; but it has since been found rather to heat and decay them, by hindering the transudation which those parts require; better supplied with loam, or strewings of brick-dust or pieces of boards; some leave a small hole for the air. But though lime be so destructive, whilst timber thus lies dry, it seems they mingle it with hair to keep the worm out of ships, which they sheathe for southern voyages, though it is held much to retard their course.

1738. "For all uses, that timber is esteemed the best which is the most ponderous, and which, lying long, makes the deepest impression in the earth, or in the water being floated; also what is without knots, yet firm and free from sap, which is that fatty, whiter, and softer part called by the ancients albumum, which you are diligently to hew away. My Lord Bacon (Exper. 658.) recommends for trial of a sound or knotty piece of timber, to cause one to speak at one of the extremes to his companion listening at the other; for if it be knotty, the sound, says he, will come abrupt."

PRESERVATION OF TIMBER.

1739. The preservation of timber, when employed in a building, is the first and most important consideration. Wherever it is exposed to the alternations of dryness and moisture, the protection of its surface from either of those actions is the principal object, or, in other words, the application of some substance or medium to it which is imperviable to moisture; but all timber should be perfectly dry before the use of the medium. In Holland the application of a mixture of pitch and tar, whereon are. strewn pounded shells, with a mixture of sea sand, is general; and with this, or small and sifted beaten scales from a blacksmith's forge, to their drawbridges, sluices, and gates, and other works, they are admirably protected from the effects of the seasons. Semple, in his work on aquatic building, recommends, that "after your work is tried up, or even put together, lay it on the ground, with stones or bricks under it to about a foot high, and burn wood (which is the best firing for the purpose) under it, till you thoroughly heat, and even scorch it all over; then, whilst the wood is hot, rub it over plentifully with linseed oil and tar, in equal parts, and well boiled together, and let it be kept boiling while you are using it; and this will immediately strike and sink (if the wood be tolerably seasoned) one inch or more into the wood, close all the pores, and make it become exceeding hard and durable, either under or over water." Semple evidently supposes the wood to have been previously well seasoned.

1740. Chapman (on the preservation of timber) recommends a mixture of sub-sulphate of iron, which is obtained in the refuse of copperas pans, ground up with some cheap oil, and made sufficiently fluid with coal-tar oil, wherein pitch has been infused and mixed.

1741. For common purposes, what is called sanding, that is, the strewing upon the painting of timber, before the paint dries, particles of fine sand, is very useful in the preservation of timber.

1742. Against worms we believe nothing to be more efficacious than the saturation of timber with any of the oils; a process which destroys the insect if already in the wood, with that of turpentine especially, and prevents the liability to attack from it. Evelyn recommends nitric acid, that is, sulphur immersed in aquafortis and distilled, as an effectual application. Corrosive sublimate, lately introduced under Kyan's patent, has long been known as an effectual remedy against the worm. Its poisonous qualities of course destroy all animal life with which it comes in contact; and we believe that our readers who are interested in preserving the timbers of their dwellings may use a solution of it without infringing the rights of the patentee. But the best remedy against rot and worms is a thorough introduction of air to the timbers of a building, and their lying as dry and as free from moisture as practicable. Air holes from the outside should be applied as much as possible, and the ends of timbers should not, if it can be avoided, be bedded up close all round them. This practice is, moreover, advisable in another respect, that of being able, without injury to a building, to splice the ends of the timbers should they become decayed, without involving the rebuilding of the fabric; a facility of no mean consideration.

1743. The worm is so destructive to timber, both in and out of water, that we shall not apologise for closing this part of our observations with Smeaton's remarks upon a species of worm which he found in Bridlington piers. "This worm appears as a small white soft substance, much like a maggot; so small as not to be seen distinctly without a magnifying glass, and even then a distinction of its parts is not easily made out. It does not attempt

to make its way through the wood longitudinally, or along the grain, as is the case with the common ship worm, but directly, or obliquely, inward. Neither does it appear to make its way by means of any hard tools or instruments, but rather by some species of dissolvent liquor furnished by the juices of the animal itself. The rate of progression is, that a three inch oak plank will be destroyed in eight years by action from the outside only." For resisting the effects of these worms, Smeaton recommends the piles to be squared, to be fitted as closely as possible together, and to fill all openings with tar and oakum, to make the face smooth, and cover it with sheathing.

1744. The destructive effects of the white ant are so little known here, that it is unnecessary to make further mention of them, than that in India they are the most inveterate enemies with which timber has to contend. From Young's Annals we extract the following curious statement of experiments made upon inch and a half planks, from trees of thirty to forty-five years' growth, after an exposure of ten years to the weather.

Whence we may be led to some inference of the value of different sorts of timber in resisting weather; though we must not be altogether guided by the above table, inasmuch as it is well known that the soil on which timber is grown much increases or deteriorates its value, and that split timber is more durable and stronger than that which is sawn, from the circumstance of the fibres, on account of their continuity, resisting by means of their longitudinal strength; whereas when severed by the saw, the resistance depends more on the lateral cohesion of the fibres. Hence whole trees are invariably stronger than specimens, unless these be particularly well selected, and of a straight and even grain; but in practice the results of experiments are on this account the more useful.

DECAY OF TIMBER.

1745. If timber, whatever its species, be well seasoned, and be not exposed to alternate dryness and moisture, its durability is great, though from time it is known to lose its elastic and cohesive powers, and to become brittle if constantly dry. On this account it is unfit, after a certain period, to be subjected to variable strains: however, in a quiescent state it might endure for centuries. Dryness will, if carried to excess, produce this category. The mere moisture it absorbs from the air in dry weather is not sufficient to impair its durability. So, also, timber continually exposed to moisture is found to retain for a very long period its pristine strength. Heat with moisture is extremely injurious to it, and is in most cases productive of rot, whereof two kinds are the curse of the builder, the wet and the dry rot, though perhaps there be but little difference between the two. They appear to be produced by the same causes, excepting that the freedom of evaporation determines the former, and an imperfect evaporation the latter. In both cases the timber is affected by a fungus-like parasite, beginning with a species of mildew; but how this fungus is generated is still a vexata quæstio; all we know is, that its vegetation is so rapid, that often before it has arrived at its height, a building is ruined. From our inquiries on the Continent, we believe the disease does not occur to the extent that it does in this country; a fact which we are inclined, perhaps erroneously, to attribute to the use of the timber of the country, instead of imported timber. Our opinion may be fanciful, but there are many grounds on which we think that is not altogether the case. Our notion is, that our imported timber is infected with the seeds of decay long before its arrival here (we speak of fir, more especially), and that the comparative warmth and moisture of the climate bring more effectually the causes of decay into action, especially where the situation is close and confined. Warmth is, doubtless, known to be a great agent in the dry rot, and most especially when moisture co-operates with it, for in warm cellars and other close and confined situations, where the vapour which feeds the disease is not altered by a constant change of air, the timbers are soon destroyed, and become perfectly decomposed.

1746. The lime, and more especially the damp brickwork, which receive the timbers of a new building, are great causes of decay to the ends of them; but we do not think that the regulations of the 19 Car. II. cap. 3., which directed the builders, after the fire of London, to bed the ends of their girders and joists in loam instead of mortar, would, if followed out in the present day, be at all effective in preventing the decay incident to the ends of timbers. Timber, in a perfectly dry state, does not appear to be injured by dry lime; and, indeed, lime is known to be effectual in the protection of wood against worms.

1747. Nothing is more injurious to the floors of a building than covering them with

painted floorcloth, which entirely prevents the access of atmospheric air, whence the dampness of the boards never evaporates; and it is well known that oak and fir posts have been brought into premature decay by painting them before their moisture had evaporated; whilst in the timber and pewing of old churches, which have never been painted, we see them sound after the lapse of centuries. Semple, in his Treatise on Building in Water, notices an instance of some field gates made of the fir of the place, part whereof, near the mansion, were painted, and had become rotten, while those more distant from the mansion, which had never been painted, were quite sound.

PREVENTION OF DECAY.

1748. After timber is felled, the best method of preventing decay is the immediate removal of it to a dry situation, where it should be stacked in such a manner as to secure a free circulation of air round it, but without exposure to the sun and wind, and it should be rough squared as soon as possible. When thoroughly seasoned before cutting it into scantlings, it is less liable to warp and twist in drying. The ground about its place of deposit should be dry and perfectly drained, so that no vegetation may rise on it. Hence a timber yard should be strewed with ashes, or the scales from a foundry or forge, which supply an admirable antidote to all vegetation. It is thought that the more gradually timber is seasoned the greater its durability; and, as a general rule, it may be stated, that it should not be used till a period of at least two years from its being felled, and for joiners' work at least four years. Much, however, is dependent on the size of the pieces. By some, water seasoning has been recommended; by others, the steaming and boiling it; smoke-drying, charring, and scorching have also been recommended. The latter is, perhaps, the best for piles and other pieces that are to stand in the water or in the ground. It was practised by the ancients, and is still in use generally for the posts of park paling and the like.

1749. In Norway the deal planks are seasoned by laying them in salt water for three or four days, when newly sawed, and then drying them in the sun, a process which is considered to be attended with advantage; but it does not prevent their shrinking. Mr. Evelyn recommends the water seasoning for fir, but we incline to think that gradual dry seasoning the best method.

1750. Notwithstanding, however, all care in seasoning, when timber is employed in a damp situation it soon decays; and one of the principal remedies against that is good drainage, without which no precautions will avail. It is most important to take care that earth should not lie in contact with the walls of a building, for the damp is quickly communicated, in that case, by their means to the ends of timbers, and rot soon follows. No expedient to guard against this contingency is so good as what are called air or dry drains, which are areas formed by thin walls round the building, with apertures in the paving laid between them and the principal walls, so as to afford a constant current of fresh air. 1751. When the carcass of a building is complete, it should be left as long as possible to dry, and to allow to the timbers what may be called a second seasoning. The modern practice of finishing buildings in the quickest possible period, has contributed more to dry rot than perhaps any other cause; and for this the architect has been blamed instead of his employer, whose object is generally to realize letting or to enjoy occupation of them as early as possible. After, however, the walls and timbers of a building are once thoroughly dry, all means should be employed to exclude a fresh accession of moisture, and delay becomes then prejudicial.

1752. We have before noticed corrosive sublimate in solution as a wash useful in the prevention of decay, and have also ourselves found that a weak solution of vitriolic acid with water will generally stop the rot if it have not gone too far. But it is extremely difficult to prevent the spreading of the fungus of the dry rot after it has once commenced; and the precautions indicated above, although not always successful, are better than the being reduced to after remedies. Certain, however, it is, that the washes we have named will often prevent the infection from spreading. Pyrolichnous acid has recently been recom. mended, and, we think, very usefully, as a remedy for preventing the spreading of the disease.

CURE OF ROT.

1753. It is no easy matter to cure the rot where it has once taken root. If it be found necessary to substitute new timbers for old ones, every particle of the fungus must be removed from the neighbourhood of such new timbers. After scraping it from the adjoining walls and timbers, perhaps no better application than one of the washes above mentioned can be employed, inasmuch as they can always be with safety applied to the parts. An extraordinary degree of heat would effect the same purpose, but this, especially in the case of floors, is difficult in application. Coal tar has been found useful, but its extremely un

SECT. V.

IRON.

1754. Iron is a metal found in almost all parts of the world, and though not mentioned by Homer, and hence, we may suppose, in his time extremely scarce, it is now more abundant than any of the other metals, and is, at the same time, the most useful. Although, with the exception of tin, it is the lightest of all metals; yet it is, when pure, very malleable and extremely hard. Its malleability is increased by heat, whereas most other metals, as they are heated, become more brittle. It is the only known substance whereon the loadstone acts, and its specific gravity to water is as 7632 to 1000.

1755. The iron manufactured in Great Britain is obtained from three species of the ore. The Lancashire, which is very heavy, fibrous in texture, and of a dark purple colour inclining to black, and lodged in veins. The Bog ore, which has the appearance of a deep yellow clay, and is found in strata of from twelve to twenty inches in thickness. And lastly, Iron stones, of an irregular shape, frequently in beds of large extent, similar to other stony masses, and often intersected with seams of pit coal. It is principally from the argil.

laceous ore or clay iron-stone that iron is extracted in this country.

1756. After raising, the ores are selected and separated as much as possible from heterogeneous substances. They are then roasted in large heaps in the open air, for the purpose as well of freeing them from the arsenic and sulphur they contain as to render them friable or easy of reduction to a powder. The roasting is performed by means of bituminous coal, and the result is a substance full of fissures, friable, and a deprivation of all vitreous lustre. After this it is transferred to the crushing mill for complete pulverization, whence it is carried to the smelting furnace for conversion into iron. Herein it undergoes two separate processes: first, the reduction of the oxide to a metallic state; second, the separation of the earthy particles in the form of scoria. These operations are conducted by submitting the ore, ordinarily mixed with certain fluxes, to the action of carbon at a very high temperature, in what are called blast furnaces, which vary in height from twelve to sixty feet, and are of the form of truncated pyramids, terminating usually in cylindrical chimneys, whose internal diameter is from four to six feet. The interior of these furnaces is usually of a cylindrical form, whose internal diameter is from four to six feet. The cavity of these furnaces is usually of a circular form, except at the crucible or hearth, where it becomes a right rectangular prism, oblong in a direction perpendicular to the blast orifices or tuyeres of the bellows. The sides of the crucible are most commonly formed of gritstone. The boshes, which are in the form of an inverted quadrangular pyramid approaching a prismatic shape, are placed above the crucible, and above them rises the conical body of the furnace, which is lined with fire-bricks, and, in ascending, is contracted similarly to the narrow end of an egg, until it terminates in the chimney. The furnace is of course constructed in the most solid manner, and strengthened by iron bands and bars. The bellows employed are mostly of a cylindrical form, and their pistons worked either by water or steam. The blast holes, which are in the upper part of the crucible, and frequently placed on opposite sides, but so that the two opposite currents may not impinge upon one another, are two in number. Openings are provided at the lower part of the crucible for the discharge of the metal and scoria, and are kept stopped by clay and sand upon the exterior when the furnace is in operation. The reduction is commenced by gradually heating up the furnace until capable of being entirely filled with fuel, and then, as its contents begin to sink, alternate changes of ore, mingled with flux, and of charcoal and coke, are added. The blast is now let on, and the metal in the ore, parting with its oxygen, flows by degrees, subsiding to the bottom of the crucible, covered with a melted slag, which is occasionally let off by removing the clay from one or more, if necessary, apertures in the crucible; and on the bottom of the furnace becoming filled with the metal, which generally occurs after nine to twelve hours, the iron itself is discharged by one of these openings into a fosse of sand mixed with clay. When the iron has flowed out the aperture is again closed, and by this method the furnace is kept in constant action.

1757. Limestone of the best quality is employed as a flux to assist the fusion of the ore, which it accomplishes by vitrefying the earths wherewith it is mixed up with the oxide of iron. The iron when run out from the blast furnace in the state of cast iron is far from being in a pure state, having a coarse grain, and being brittle. In its conversion to bar iron, it undergoes one of the two following processes, as charcoal or coke may be employed. In the former case a furnace much resembling a smith's hearth is used, having a sloping cavity sunk from ten to twelve inches below the blast pipe. After the cavity has been filled with charcoal and scoria, a pig of cast iron, well covered with hot fuel, is placed opposite the blast pipe. The blast being introduced, the pig of iron lying in the very hottest part soon begins to melt, and runs down into the cavity below, where, being out of the influence of the blast, it becomes solid, and is replaced in its former position, and the