plummer-blocks be set somewhat out of truth, the ball and socket joint allows the bearings to adjust themselves in line. The base of plummer-blocks and the face of sole-plates and wall-boxes should in all cases be planed, as any little outlay in this way is amply repaid by the

shafting running truer, and being less likely to get out of line. All parts of a plummer-block should be turned and planed together.

Our illustration (Fig. 7) represents the section of a plummer-block such as we have described, and which will be found to answer well. A further improvement in its construction, over ordinary bearings, is the simple arrangement for lubrication. This consists of a dovetail slot running nearly the whole length of the top half of the bearing, which is packed in with cotton and saturated with oil, and being constantly in contact with the shaft, a film of oil is spread over the whole wearing surface of the bearing. Hanging brackets and bearings should in all cases be planed and turned together.

In fixing shafting, it is important that it is made to run at a dead level; this can be best done by means of a straight-edge and spirit-level. In the first place, take the straight-edge and rest it on the bottom bearing of two or more of the plummer-blocks, and pack them up till the spirit level stands exactly true, then try the shaft in several places. Care must be taken that the driving pulleys on the main shaft and the pulleys on the machines or countershafts are exactly linable with each other. This can be ascertained by means of a long straight-edge, by placing it to bear evenly on the edges of the driving pulley and setting the other pulley to it; if the driven pulley is some distance off, in the place of a straight-edge, a plumb-line or piece of string may be used in a similar way: this gives you a line at right angles with the shaft. One shaft can be set at right angles with another by using a square on the main shaft and by stretching your plumb-line from it. The main shaft should, in the first instance, be set from the driving wheel on the engine, and not from the walls of the building, as is sometimes done, as these may run out of truth; the engine, however, should be set as nearly parallel with the walls as possible.

Cross shafts, vertical shafts, and toothed gearing should in saw-mills be avoided as much as possible, and one line of horizontal shafting should not be set above another in a perpendicular line, as the driving power of the belt under these circumstances is lessened. Lengths of shafting should be calculated so that as far as possible, when erected, the couplings should come close to a bearing.

When several lines of main shafting running parallel to each other are in use, the pulleys receiving and transmitting the motion are best placed close to each other on the same side of the mill, with bearings well up on either side of them; the strain on the shafts is thus more equalised, as the belts pull in both directions.

Wherever practicable, we prefer the shafting to be mounted on standards and fixed under ground, but where it is necessary to use hangers, the bearings should be made adjustable for wear, &c., in all directions in the plane of the shaft's rotation. If wall brackets are used, the bearing may be made adjustable transverely by making the plummer-block or pedestal separate from the wall bracket, and mounting it on an adjustable pin made to pass through a hole in the hanger, and through another hole formed in the base of the plummer-block. If ordinary plummerblocks are employed, the holes for the holding down bolts may be made slightly oblong in a direction transverse to the shaft, which will usually allow of all the side adjustment necessary. Heavy, cumbersome hangers and wall

brackets should be avoided. Collars should be fitted to all shafts to prevent end play; these are best placed one at each end of the shaft inside the last standard or bearing. Where large power has to be conveyed from one shaft to another in close proximity, mortise or cog wheels, or friction gear, may be used with advantage; if the speed is not too great, we prefer mortise wheels. Wooden cogs

should be about one-third thicker than the iron teeth of the wheel with which they are engaged; they should be made somewhat shorter and thicker at the root of the tooth than ordinary wheels.

Care should, however, be observed in shortening the teeth that the arc of their contact is not too much reduced. In practice involute teeth are found stronger than cycloidal. If cast-iron wheels are used the teeth should be very accurately moulded and finished, and for high speeds the wheels should be made about one-third wider on the face than for slow speeds. In comparing belt with toothed gearing for transmitting power, the balance, except under especial circumstances, is in favour of the former, and much more so if the gearing is worn or badly proportioned.

In small wheels and pinions, where considerable strength is necessary, the teeth should be "shrouded."

All pulleys should be accurately turned and polished, and driven pulleys rounded somewhat on the face, and perfectly balanced. This latter is especially necessary for pulleys used in a saw-mill, owing to the high speeds at which they are run. The pulleys should be as light as is compatible with strength; some of the wrought-iron pulleys lately introduced will be found very serviceable. Main driving pulleys, which transmit a large amount of power, should be of extra strong section, and in some cases should be constructed with double arms. The metal of the bosses of all pulleys should be proportioned to the size of the shaft on which they run, in order to avoid superflous weight. Ordinary loose pulleys should be made with a boss of at least twice the length of that of the fast pulley.

In erecting countershafts they should be fixed, as far as possible, so that the belts pull on the main shaft in opposite directions, as should too many belts be pulling in one direction, and the shaft be of insufficient size, or not very strongly supported, it will cause a great deal of trouble by springing, and will soon get out of line. In fixing driving pulleys on the main shaft, those transmitting the greatest power should be fixed as near to the bearings as may be practicable. If hangers from the roof are employed, they should be mounted on substantial hard-wood plates of a sufficient length and width to give an ample bearing surface to the base of the hanger. Countershaft bearings, as well as main shaft bearings, should be made adjustable for wear and alignment.

In conclusion, we may say wherever possible we prefer to use belt gearing instead of toothed, as in the first place toothed gearing requires more power to transmit the same effective force than belts; it is also unsuitable for high speeds. We think, owing to their strength and lightness,

wrought-iron pulleys ought to be, and as they become better known probably will be, largely adopted. If from the exigencies of the site or other cause it is necessary to run a shaft at an angle to the main shafting, we prefer a belt led over guide pulleys instead of a cross shaft and bevel wheels, as it is less noisy, much cheaper, and, if well arranged, quite as effective. The best plan with which we are acquainted is to mount the idle pulleys on a spindle fixed vertically in a ball and socket seating, which may be fitted in a bracket attached to a hanger or standard by prolonging the end of the spindle and fitting it with a screw, serrated washer, and nut; the spindle and pulley may be set at any desired angle. The spindle carrying bracket should be so arranged with a vertical adjustment on the hanger or standard. The ball segment of course can be turned round, as may be necessary, and, with the plan we have sketched, the idle pulleys may be adjusted to suit any position of shaft, thus obviating the construction of a special set of hanger or bracket patterns for each separate case, and at the same time ensuring the correct running of the belts on the main pulleys.

We insert some useful hints as to fixing shafting given by a correspondent of the Mechanical World, who says:"To fix a line of shafting in a direct line with an existing shaft, commence by fixing securely a wooden bracket on the wall, standard, or column, similar to that we have shown in the accompanying figure. Be careful to see that the top of the bracket is level, and also exactly level with the centre of shafting. When this bracket is fixed correctly, then, with a truly parallel straight-edge, level on to where it is decided to fix the first permanent bracket; now fix another wooden bracket close to, but not interfering with, position of bracket, and so on, as far as may be necessary. These temporary brackets will enable you to set-off the proper positions of the permanent brackets accurately, and