Though circumstances require certain dispositions of tim bers in a building, the timbers will still admit of infinite decoration, without injury ; and sometimes so much as at first view to conceal the principal use. In the middle ages, carpentry partook of the style of building called Gothic; the roofs were pitched very high, but were frequently deffctive, On account of the want of tie-beams, which were omitted in order to obtain more lofty ceilings; height being one of the predominant features of this species of architecture.
Carpentry has been cultivated by the modern Italians. Seidlo, in his first book, exhibits a construction for naked flooring, with timbers shorter than either of the dimensions of the area to be covered ; in the fourth book he shows some very curious and strong methods of framing doors, according to the principles of trussed work ; and in the seventh book, he has some very good forms for the trusses of roofs. The wooden bridges of Palladio arc most excellent examples.
Among the French, the construction of wooden domes has been improved by Philibert Delorme, and Moulineau ; and the centerings of arches and bridges by Perronet.
In England, the very curious construction of naked floor ing, exhibited in the works of Serlio, has been demonstrated and improved by Dr. Wallis, and carried into execution, in the theatre of Oxford, by Sir Christopher Wren, who also designed the wood trussing of the dome of St. Paul's, and contrived a very curious scaffolding, which supported itself without anything below it, for the purpose of building and painting the interior dome. The art of carpentry has been much cultivated of late years in England, so that it has now begun to assume a scientific form. In accuracy and celerity of execution our workmen are unequalled.
Of late years the. improvements in the manufacture of iron, both cast and wrought, have caused the introduction of that material into buildings in every variety of form—as girders, beams, &c. The floors, and sometimes even the roofs of those intended to be secured from fire, have been constructed of iron ; and iron hooping is now used instead of bond.timbers in walls. The use of this material, how ever, as a substitute for wood, does not change the principle, as both materials are affected by the same gravitating laws.
The operations to which timber is subjected, from the time of its arrival in the carpenter's yard, in its natural state, to the period of its final employment in a building, may be classed under two general heads; as, those which relate to individual pieces, and those that relate to their connection with others.
Under the first head is the pit-saw, by which whole pieces of timber are divided, and reduced into scantlings. This term (from the French, enchantillon) means the dimensions in breadth and thickness, without respect to the length.
Planing is the operation of reducing the wood to a smooth surface, by means of an instrmnent called a plane, which consists of a chisel fixed in a frame, serving at once as a handle and a regulator to the edge, which cuts the wood in thin shavings as the plane is moved to and fro by the work man. The operations of the plane, besides that of reducing timber to a uniform surface, are those of grooving, rebating, and moulding: the latter not being necessary in earpentry, we shall only describe the former two : Grooving is the reducing a piece of timber below the surface, so as to take away a prism, and thereby leave a channel consisting of two surfaces of equal breadths, and another surface, of equal breadth, joining the other two, parallel to the surface from which the recess is made, generally forming two individual right angles.
Rclmating is the reducing of a piece of timber, by taking away a prism at the angle, so as to leave only two sides, each of a parallel breadth, forming an internal angle, gene rally a right angle : so that in grooving and rebating, the groove or rebate is always less than the original depth of the stuff or piece out of which it is firmed. Time latter operation is particularly used in door-cases and the frames of easement-windows ; the rebate forming a kind of ledge for the door or casement to stop against.
The implements which the carpenter has occasion to employ in the several operations, \rill be seen under the head 'foots.
The principal operations, after the pieces are formed, consist in the joining or timbers: two pieces of timber may be joined so as to form either one, two, or fiatr angles, oblique or right. A notched joint is formed by cutting nut of the thickness of each piece, a part in the tbrin of a parallelopiped ; so that when the two pieces are joined, the substanee left at the reduced thickness of the one piece, fills the excavation of the other, as far as it goes into its depth. If the thickness of the part left be equal to that of the part taken :may in each piece, and the thickness of the part left of the one piece be equal to the thickness of the part left of the other piece, the joint is then said to be halved. In malting one angle, the excess or excavation is formed at the end of ,:tch piece, and consists of two plane surfaces, one perpendicular, the other parallel to the two opposite faces, and in the plane of the angle. III funning two right angles, one piece must, of course, project on both sides of the other, and the other, only on one side ; the excavation or recess made in that which projects i01 both sides, consists of three plane surthecs, one being parallel, and the other two at right angles to the faces ; the excavation or recess made in that which projects on one side, consists of two plane surfaces, in the like positions. In forming firur right angles, the notch of each piece consists of three sides, two of which are at right angles, and the other parallel to the flees. One piece of timber may also be joined to another, so as to form only one or two adjacent angles, by mucking one piece on three sides at the ends, and so thrilling a projecting prism, called a tenon, the sides of which are respectively parallel to the sides of the piece, and by excavating the end of the other piece, to receive the tenon, which is made to fit exactly. The two pieces thus formed at one or more angles to each other, may, if found necessary, be fixed by means of wooden pins, or nails, spikes, screws, bolts, straps, or other metal firstenitigs.