on its lower edge being formed of the corresponding shape, as at ƒƒ; the side elevation of this is shown at g, and a cross section on the line h h at i. Wall plates are joined together in the direction of their lengths by the "half lap" joint at ab, fig. 11, and at the corner of the wall,

d

a

b

e

3/2 Fig. 11.

as at c, by the same half lap joint, of which a side elevation is at d, one of the plates at e, or they may be joined by the "mitre" joint, as at f. Joists are jointed to "trimmer joists" (see fig. 9, Plate IV.), by the joint, in fig. 12; the

tenon a, in place of stopping short as at the dotted line, may be extended through the trimming joist, bb, as at c, and secured by a "pin" as shown;

the front of trimmer is shown at e e, with the joint cut into

its face.

The ends of "binding joists" are secured to the

faces of "girders by a joint of the same kind, which is called a "tusk tenon," as illustrated at ee in fig. 11, Plate IV. The usual depth of the tenon, e, is one sixth of the whole depth of the binding joist; and the plate of the tenon, e', is one third of the depth of the joist measured from its lower side. The "ceiling joists," c, fig. 4, Plate V., are joined to the "binding joists," as shown in fig. 13, where a notch, a, is cut out of

the lower edge of the binding joist, b, into which the ceiling joist, c, is passed; d d shows the under side of binding joist with notch, e, cut out of it; f, cross section of do., with ceiling joist,g. Another method is adopted in which a chase, or sunk part, is cut, in a horizontal direction, out on

d

d

Fig. 13.

one face of the binding joist, near its lower edge, the end of the ceiling joist, a, being provided with a projecting part or tenon passing into the chase or mortice, ƒƒ.

are

5. Lengthening of Beams.-Where "tie beams required of such lengths as prevent them being in one piece, two beams are lengthened by joining them in various ways. We shall at present illustrate one or two of the methods in use, describing others in a succeeding part of this volume. The simplest and the strongest mode of joining two timbers together in the direction of their length is what is known as "fishing." this the two beams, a and b, fig. 1, Plate V., to be joined, have their ends carefully squared off, and made to butt against each other at c c; they are kept together and secured by the flat pieces of timber, d d, e e, one placed at the upper, the other at the lower edges of the two beams; bolts, ff, pass through the "fishing

In

pieces" d d e e, and the beams a b, and are secured by nuts at the end; the nuts should be screwed tightly up, as on these depend the strength of the joints. As they are apt to be incrusted into the wood, plates of iron are sometimes placed beneath the bolt-heads and the nuts, or in place of the fishing pieces being of timber, as in fig. 1, they are of iron, as shown in fig. 8, at a a. Usually two fishing pieces are employed, as in fig. 1, Plate V., and shown in section in fig. 4; in some cases, however, fishing pieces are placed at the sides of the beams, thus enclosing them, as it were, and as illustrated in fig. 5, where a is the beam, b the lower, c the upper, d the left hand, e the right hand fishing pieces, and secured by the bolt and nuts. As said above, the method of "fishing beams" is the strongest employed, but it is obviously unsightly and clumsy, in consequence of the projecting parts as d de e, fig. 1, Plate V. To avoid this, the fishing pieces are sometimes let in to the surface of the beams wholly, as at bb, fig. 8, Plate V., or partially, as at c c, same figure; but this method, although adding to the sightliness of the joint, greatly takes from its strength. Other methods are, therefore, adopted where appearance can be gained without sacrificing the strength of the joint too much. The principal upon which those other joints are made is that known as scarfing, which enables the joint to present a smooth, or rather flush appearance on all sides. The simplest form of scarfed joint, known as the half lap, with flat or rectangular "tables," by which term the projecting parts or scarf joints are designated, is illustrated in fig. 10, Plate V. In this a part is cut out at the end of each beam, equal in depth to half of the full depth of beam, and of length equal to the required length of scarf. The two ends, when brought together, form the joint, as in fig. 10, the projecting part of one, as a, falling into the recessed part, b, of the other. The two are secured together by the timber or iron plates c c, d d, and by screw bolts and nuts. The plates are better when extending beyond the ends of the

joints, as shown by the dotted lines. The iron plates should be provided with angular ends, as shown at d, in fig. 8. A very common form of scarfed joint, with angular or oblique "table," is illustrated in fig. 14, where the meeting faces of the two beams, a

and b, is oblique, as at c c; the ends being indented angularly, as at de; the two being secured together by the plates, ff, g g; a better form of fishing plate being, however, as illustrated at a a, fig. 8, Plate V., the plates extending beyond the joints, as in dotted lines in fig. 10, Plate V. Another form of scarfed joint, with two tables, is illustrated in fig. 15,-a b, the two beams; c c, the

oblique tables.

1/2 Fig. 15.

In addition to the screw bolts, and nuts, and plates, d d d, a wooden "key," e, is driven into a groove cut to receive it; the key is of hard wood. Keys are sometimes added to the scarf with plain table, as in fig. 10, Plate V., at the dotted lines e e.

6. Increasing the Depth of Beam.-Where beams are required to be of greater depth than can be conveniently obtained by a single beam, two beams are laid edge to edge, and secured in various ways. Fig. 16 illustrates one method known as cogging, caulking,

or keying A series of grooves, as a a, fig. 17,-which is a plan of the upper edge of the lower beam, b b, in fig.

16,-are cut in the edges of the beam, at equal distances, as shown, and keys or cogs, c c, driven into the grooves. These prevent all lateral or side movements of the two

d

Fig. 17.

beams, a a, b b, upon one another; and the beams are secured and kept together vertically by the screw bolts, d d. In place of these, straps, as e e, are sometimes employed. These are also sometimes used in place of bolts in scarfing of beams, already illustrated in Plate V. Fig. 2, Plate V., is the plan of upper edge of the fished beam in fig. 1; fig. 9 the plan of fig. 8; fig. 11 plan of fig. 10; fig. 6 section of fig. 8, on line a b'; fig. 7 section of fig. 10, on line a b'. The scale to which all the drawings in Plate V. are drawn is "half-inch to the foot."

7. Increasing the Thickness of Beams.-When beams are required to be of great thickness, in place of employing one very thick beam, two beams are used, laid face to face, and strengthened either by inserting a flitch or plate of wrought iron between the two beams, and securing them together by screw bolts and nuts, or by what is called trussing them. These methods are illustrated in Plate VI., fig. 1, being part elevation of a "flitch" beam (sometimes also called a "sandwich"