rods, crank and crank-shaft are made of the best steel, so as to combine strength with comparative lightness.

Circular Saw with Steel Travelling Table for breaking down logs of round or square timber into scantlings, &c. The timber is carried to the saw upon a steel bed, running on rollers with iron spindles, at rates varying from 12 ft. to 40 ft. a minute; and the table has a quick return motion of 150 ft. a minute. The travelling bed is fixed nearly level with the floor of the mill, so that the timber may be readily placed on it. The log needs no fixing, as its weight keeps it steady upon the table. All the gearing connected with the feed and return motions of the table is attached to the main bed of the machine, thus making the machine entirely self-contained (Fig. 270).

Horizontal Frame-Saw.-The timber is carried on iron transoms bolted to steel joists, and provided with dogs or clips at suitable intervals. The saws and their driving gear can be raised or lowered to save time lost in adjusting the machine after each cut, and the whole of the driving gear for the saws is attached to one saddle. The connecting rod is attached to the swing frame in the middle instead of at the end to reduce the space taken up. The feed has several changes of speed, and is driven directly from the crank-shaft (Fig. 271).

Horizontal Endless Band-Saw.-This saw, protected by the Landis and Ransome patents, represents the highest development of timber-sawing machinery in Britain at Fig. 270.

present. It can be used both for slabbing or breaking down logs, and for cutting boards or scantlings; and it can make a true cut through the centre of an Elm log 20 ft. long by 3 ft. in diameter in less than a minute. As only two belts are required to work all its motions, it can be driven by a portable engine for sawing large timber in the forest. It is constructed entirely of metal, and is fixed on a ground-level bed of concrete, without excavation. The saw-blade runs at a speed of about 7000 ft. a minute, and is carried on a pair of large, well-balanced steel pulleys, the saw-blade running on the metal rim with the teeth projecting sufficiently beyond the edge to clear the set. The saw is supported close on each side of the log by passing through adjustable hardwood guides, which can be instantly moved nearer or farther apart, to suit logs of varying widths, by turning two small hand-wheels carrying pinions gearing into horizontal racks on the main saw carriage. The feed ranges from 4 to 80 ft. a minute, and is driven by a simple friction gear, controlled by a switch-handle, by which the rate of advance can instantly be varied. The backward motion of the carriage is 400 ft. a minute, and is also worked by friction gear operated by another lever, which enables the sawyer to start, stop, or reverse it at once. The sawyer directly controls the whole machine. On his left is a hand-wheel with indicating disc, by which the thickness of the board to be sawn is regulated, and at his right hand, arranged in a switch rack, are four levers which respectively (1) start and stop the saw; (2) start, stop, and reverse the timber carriage; (3) work the self-acting rising motion of the saw; and (4) vary the rate of feed. The travelling-carriage for the log consists entirely of metal, the main sides being rolled steel girders connected by

cast-iron stretchers. It is accurately planed on both upper and under surfaces, and runs on a series of turned rollers revolving in carriages bolted to the floor. Each of the castiron stretchers has an adjustable wrought-steel dog-cramp worked by screws from either side of the carriage. The carriage is moved backwards and forwards by means of two steel pinions working into corresponding racks under each main side girder.

Fig. 272 represents a new type of single blade, 18 in. horizontal log frame, for small sawmills. It is specially designed to resist the strain due to the reciprocation of the sawframe; consequently a greater number of strokes can be made per minute, and a larger amount of sawing done.

The framework is on a cast-iron bedplate, and the saw-frame carriage rises and falls on two strong cast-iron standards, having planed faces and adjustable strips for taking up

wear.

Horizontal Endless Band-Saw.

The saw carriage rises and falls by means of two screws worked by a large handwheel. The swing-frame crossheads slide between gun-metal strips adjustable for wear, the thrust of the cut being taken by strong thrust-blocks. The saw is steadied by guides placed immediately each side of the timber. The crank-shaft, fitted with a pair of fast and loose pulleys, is mounted on two strong cast-iron standards, and the shaft runs on two long bearings of hard gun-metal, adjustable for wear. While being sawn, the timber is held down on the travelling-carriage by adjustable steel dogs.

It is not here necessary to give full descriptions of these, or of other very expensive and powerful sawing machinery for large timber mills, because precise details regarding such important points as price, size, weight, horse-power, diameter of driving-pulley, speed of crank-shaft and saw, length of travelling bed, dimensions of logs that can be slabbed, broken down, or sawn up, &c., are easily obtainable in full in the catalogues of firms making a specialty of this class of machinery-e.g., Messrs. A. Ransome & Co., Newark

on-Trent and Chelsea (who have kindly enabled me to reproduce Figs. 269 to 272); Messrs. T. Robinson & Son, Rochdale; and several others both in Scotland and England. And in such catalogues will also be found ample details regarding saws, and the machinery for stripping, re-setting, sharpening, brazing, and mending mill-saws of all kinds by machinery, together with various kinds of labour-saving appliances, such as haulingapparatus, log-turners, overhead travelling crabs and cranes, &c.

For ordinary estate purposes, however, machinery of the above kinds is mostly too expensive, although where there is the prospect of converting continuously on anything like a large scale it is always economy to get the very best class of machinery, even though it may cost a larger capital outlay to start business operations. Such machinery will, however, always need to be in charge of an experienced engineer, and the simpler class of saw-mills that may usually be worked under the direct supervision of the forester will consist of vertical framesaws or of circular saws driven either (1) by an overshot water-wheel, or (2) by light steam-power provided by a small stationary yard-engine, a portable engine, or a traction-engine in the charge of a trained hand. Given a favourable supply of water, water-power is by far the cheapest method of conversion, but it is only by the use of a portable or a traction-engine that a saw-mill can be moved from place to place in or near the woodlands. The cost of erecting a small mill with a full complement of simple but good workable machinery may vary from about £300 to £500 up to £1000 or more, according to its class, working-capacity, and quality. The initial cost of a small mill, purely for estate purposes, is of course greater when a traction-engine is required.

ひ

Mill-saws act on timber in similar manner to hand-saws, though of course at a very different rate, so that what has elsewhere been said about these (see p. 468) also applies generally to the former. But the shape of the teeth is usually different, and the saws have to be made of the very best steel, a very high quality being more especially important for all frame, circular, or band-saws driven by steam machinery at a great rate of speed. For frame-saws the teeth are generally somewhat J-shaped on their face, thus— the sharp, slightly hooked points facing in the cutting direction. The teeth of circular ripping-saws (see Fig. 280, p. 576) are more or less hooked at an angle varying from 20° to 30° from the radius of the circular saw, the amount of hook being greater for soft than for hard timber. The teeth of cross-cutting saws are made without hook, being usually of an arrow-head shape rising from a broad base. The pitch of the saw, or distance from tooth to tooth, is also greater in circular ripping-saws than in cross-cutting saws, and may vary, according to the diameter of the saw, from about 1 to 2 in. in the latter to 1 to 2 in. in the former, saws for softwoods requiring more pitch than those for hardwoods (see Fig. 280). The shape and the pitch of the teeth of course regulate the proportion between the tooth-area and the kerf for holding and extracting the sawdust, which ratio generally varies from about 12 for hardwoods and 1:3 for softwoods. So, too, the set of the teeth to each side alternately is greater for soft than for hard wood. The teeth of band-saws are usually shaped differently from either of the above, thus

Mill-saws should be made of the finest cast steel, and their thickness and size should be proportionate to the class of work they are intended to perform. The thinner the saw, the easier it is to drive, and the less wastage there is as sawdust;

but when worked at high speed the tension becomes greatly increased, and too thin a saw will not cut true and straight, while it may easily buckle or break. The gauge will therefore vary from 12 to 16 according to circumstances. Thus, thinner saws of higher gauge will suffice for softwoods and non-resinous Conifers than are