thrusts and in which the timbers a and b are held together by two keys cand c. Usually scarfed joints are strengthened

by means of iron or wooden plates called fish-plates, and when these are set into the wood in such a manner as not

to increase the size of the timber, it is still a scarfed joint; but when the pieces used for joining the timbers are simply

bolted on to the outside, as illustrated in Fig. 19, the joint becomes a pure fished joint, and the plates c and c are called fish-plates.

49.

Heavy Framing by Cutting Joints.-One form of heavy framing is illustrated in Fig. 20. The heavy sill timbers a are secured to the timbers b by notching into each timber, as shown in the illustration, and also by the use of drift bolts. The posts c are fastened to the timbers b by means of tenons and treenails, or pins. The timbers for the second floor e and d are united by notching and by drift bolts, while the posts ƒ for the next upper story are secured by tenons and treenails. The braces g are notched into the posts and sills and secured by heel tenons and pins.

Fig. 21 illustrates a tenon on the end of one of the braces. The floors may be formed by using a joist i the same depth as the timbers b and notching

FIG. 21

them on to the sills a to the same depth the timbers b were notched down. After this the floor k can be laid on top of the joist and the timbers b. Where the braces do not extend the full width of the post, they can be placed either flush with the outside of the building, as illustrated, or centrally on the timbers. The manner of placing the braces flush with the outside as illustrated has the advantage that whatever form of siding is used, it will be secured to both the posts and the braces, and will thus aid in stiffening the building.

50.

Heavy Framing Without Cutting Joints.Fig. 22 illustrates another system of framing which is to a large extent on the balloon-frame order, for it has no mortiseand-tenon joints and very little framing of any kind. The sill timbers a and b may be notched together and secured by means of drift bolts; the posts may be slightly notched into the timbers b and secured by drift bolts. The braces g are simply pieces of plank cut and spiked as shown in the

illustration, the pieces

being spiked against the posts or sills in such a manner as to fill the space between the ends of the braces. Where the floor joists m rest upon the sill a, it may be necessary to use a narrower piece between the braces, as at i, or to saw notches into the piece i, into which the joist can be placed. The timbers d and e for the upper

floor of the mill are fastened together and to the posts f and c by slight notching and drift bolting.

In some cases sawed off square

no notching is done, the posts simply being and secured by large spikes or drift bolts. The floor in this - style of construction is laid exactly as in the previous case and is shown at k

51.

Corbels. Where it is necessary to join sills or

large horizontal timbers on top of posts, corbels may be

used, as shown in Fig. 23.

The corbel a is bolted to the two timbers b and c, and the post d is usually tenoned into the corbel, while the post a may have a wide tenon and be secured to the timbers b and c by means of two treenails or pins. By making the corbels fairly long, they will help support the timbers b and c, thus relieving them of a portion of

FIG. 23

the weight they would otherwise have to carry.

a

On this

account, corbels are sometimes used whether joints occur above the corbels or not.

1

THE STAMP MILL

52. The gold stamp mill has been described in Ore Dressing and Milling. Fig. 24 shows one, in cross-section, situated on a side hill, for the convenience of receiving its ore by tram cars that dump over a grizzly. The ore that passes over the grizzly passes to a crushing floor and thence. through a crusher to the ore bin, where it again mingles with the ore that passed through the grizzly. From the ore bin, the ore passes through a gate into an automatic ore feeder, which supplies a stamp battery composed of five stamps. The crushed ore passes from the stamp-battery mortar, as pulp, over amalgamating plates; then from the launder at the foot of the plate it passes to concentrating tables, an arrangement not used with free-milling ores, but quite natural with a rather refractory ore.