When binding joints are framed into girders, as they have to support the bridging and boarding of the th mi., there will he a considerable strain at their extremities ; in order to make the tenons sufficiently strong to resist the weight, they should be framed with a shorter bearing tenon attached to the principal tenon and a sloping shoulder above, called a task ; tenons thus fiTmed are (railed !HA. tenons.
When two parallel pieces. quite immovable. are to have :mother piece framed between them. proceed thus :—Insert the one eit 1 of the tenon of the conneeting piece into a shal low mortise, and make a long mortise-ill the opposite side of the other timber. so that when the cross, piece is moved round the shoulder of the other extremity, as a centre, it may slide home to its situation : thus if' the tenon at the movable end lit the mortise closely. the bottom of the mor tise would be the are of a circle, of the shoulder of the tenon first formed would he the centre : but the bottom of the mortise may be straight instead of circular. pro vided it lie sufliciently recessed to clear the end of the pieee. This mode of framing a transverse piece between two others is employed ill trimming in ceiling joists : the bindinri joists are always previously mortised befbre they are disposed in a situation to receive them. and the ceiling are seldom or never cot to their lengths and fitted in before the building is covered over.
When a transverse piece of tinlher is to he framed bet ween two parallel joists, of which the vertical slirfi•es are not parallel, turn the upper ed..te of the transverse piece down wards upon the upper horizontal surface if the joist.: mark the interval or distance between them upon the surface of the transverse now under; then writ the 1 rall•VeNe piece in the way it is intended to be framed, placing I he edge over the places where it is to let down ; then apply a st•aight-edge to the oblique surface of the joist, and slide the transverse piece so as to bring the mark upon the upper side of it in a line with the st•aight-edge. This being done, proceed in the saint. manner with the other end, and the two lines drawn on the vertical sides or the intermediate piece ill mark the Amide' s of the tenons. This process is called by workmen tootblin-in joists. and is particularly useful when the thither is warped or 1 laving shown the principles of lengthening timber and of beams. also the methods of joining timbers
at angles, we shall now proceed to construction in general.
In groin centering. the boarding which forms the exterior stirthee for building 0140 is supported by transverse ribs of timber, which are eith, r sing dy. or with trusses, according to the magnitude of the work ; and as a groin con sists generally Of two vanits crossing each other. one of them is always boarded ov, r. the same as a plain vault, having any resi c t t to 11,e (Alm, which is utter wards ribbed tied bearded. so as to make out the regidar surface.
Timbers disposed in walls and at returns or angles, are joined together whene the magnitude of the building, or exposure to strain, 'nay require. These are of three denomi nations, as bond-thober. lintels. and wall-plates.
Flooring is supported by one or more rows of parallel beams. called hoked or carcoe-floorino. and is denominated either single or double, accerdingly. The manner of joining the tinihers we have already spoken of.
During the construction of the building, the flooring of carpentry, it' not supported by brick or stone pattitions, is either supl of ted by the partitioning of timber or by shores. The ciurst•urtion of the flooring, whether single or double, depends the magnitude of the building, the horizontal dimensions of the apartments, or the weight w hich the board ing may be required to slipport. When the flooring is retrired to he very stiff, it becomes necessary to use truss girders.
Naked II4,oring for dancing upon should he made very strong, and so contrived that the upper part of it may spring, so as to benol to the impression the force, while the lower part, sustaining the eriling, remains inme)yal)le.
Partitions arc constructed of a row of timbers, or if the length of the bearing require very great stiffness, they are made of framed t•uss-work, and afterwards filled in with parallel timbers. The trussing of partitions may be made to assist in giving support to the floors, where they are unsupported below. The framing ought to be so managed as to discharge the office of hanging up the floor, in what ever situation the doors are placed. Truss partitions are also of the utmost use in supporting the superior floor.