accurately balanced. They should never be worked at short centres; and all driving belts should be of ample width; the transverse strain, which is so destructive to bearings, is thus minimised, and the cost of belting and lubrication reduced. Steel is to be recommended for spindles in preference to iron, on account of its homogeneity and rigidness. By its use the diameter of the spindles can also be reduced considerably-say, about one-fourth.

In machines whose cutter blocks have only one bearing immediately supporting it, such as overhungcutter moulding machines, vertical-spindle shaping machines, &c., the superior rigidity of steel is especially valuable, as, should the spindles spring from the excessive pressure which they are sometimes subject to, the bearings are rapidly destroyed and the work turned out is of an inferior description.

'Footstep' bearings, or those on which the lower ends of a vertical spindle rest, are usually solid, a cup- or obtuse V-shaped recess being turned in one end of the bush in which the spindle revolves; sometimes, however, conical bearings are substituted. In either case these bearings should have both lateral and vertical adjustments; and, as the dust made in working necessarily absorbs much of the lubricating matter, a recess for oil having direct communication with the bearing surface should be formed in the pedestal in which the bearing is fitted. Should a bearing become heated or 'seize,' pour cold water on it till thoroughly cool. This heating often occurs with new bearings, and may arise from several causes-viz. want of lubrication, the bearing or spindle being out of truth or badly fitted, from a 'seamy' spindle or the bearing being

screwed down too tight. Should the bearing be much abraded by the friction, it will be necessary to remove the spindle and 'scrape' the bearing before restarting. The level of the spindle should be tried, and the bearings well lubricated; the cap screwed down lightly, and the spindle worked for a short time without performing any duty.

If conical bearings are used care must be taken that the spindles are allowed no end play. This can be secured by fitting a steel pin, screwed at its own end and passed through the end of the bearing till it touches the end of the revolving spindle. The steel pin can be set up by a nut, and the end nearest the spindle should be of somewhat smaller diameter, and a flat filed on its side, which will form an efficient oilway.

In practice it is often found more difficult to keep bearings well lubricated that are subject to constant and great pressure than those which carry spindles revolving at high speeds, as, from the weight of the load, after running a short time their unguents are expelled from the bearings unless especial provision is made. For this class of bearings unguents with a metallic base, such as plumbago, are found the most efficient. A dry metallic composition has recently been introduced for lubricating purposes; it is made in the form of small cylindrical plugs and inserted in holes made in the solid bearings or surfaces requiring lubricating. It is reported to bear a temperature of 450° Fahr. It is known as 'metaline,' but we cannot from our own experience speak as to its value.

CHAPTER XXXIV.

MACHINE FOUNDATIONS.

THE proper fixing on adequate foundations has much to do with the satisfactory performance of wood-working machinery. In the case of machines working on the rotary principle little difficulty is experienced as regards foundations, the stress being as a rule easily absorbed by well-apportioned framing—that is, on the assumption that the working parts are all truly balanced and fitted. With machines with a reciprocating action, however, it is different; considerable difficulty is sometimes found in arranging them to operate with a minimum of vibration.

Conditions sometimes arise in consequence of proximity to tidal rivers, or on undrained land, where, before a machine requiring a deep foundation can be fixed, especial means must be taken to get, in the first instance, a solid basis. Where the water is very troublesome and difficult to get rid of, and where the weight to be supported and vibration to be absorbed are considerable, as in the heaviest class of log-sawing frames, we have found a series of English elm piles to make the most durable and satisfactory foundation. The distance apart, and the depth they should be driven, must depend on the action of the machine, the weight of the load,

and the nature of the soil. The tops of the piles should be sawn off level, and sleepers or planks fixed transversely on the top of them. This will make a safe and lasting foundation. The piles and sleepers should be creosoted. It is also advisable that the machine should be fixed on an extended bed-plate of extra massive section. When the ground is moist only, and much concrete is unnecessary, a good plan is to ram the substratum firm, and cover with a layer of broken stone or slag to about 6 inches in depth. Into this layer pour melted asphalt. This, when cold, binds together in one solid mass, prevents damp, and gives a strong foundation for the subsequent masonry.

To reduce the depth and lessen the cost of excavations, saw frames should be connected to the crank shaft by two rods, one on either side of the frame. The vibration is also reduced considerably by counterbalancing the reciprocating parts, and by arranging the crank shaft as near the base of the machine as possible; with saw frames a fly wheel or wheels is found to add considerably to their steadiness in working. If the saw frame is fixed on masonry, we have found the vibration considerably lessened by the introduction of a sheet of lead or a thin piece of hard wood between the base of the machine and crank-shaft plummer-blocks and the masonry. As regards the masonry employed, stone is of course stronger and more solid, and offers a better resistance to vibration, than any other, but its greatly increased cost is somewhat of a bar to its general adoption for all classes of machinery. The strength of a stone foundation depends in a great measure on the quality of the stone employed, and also that the size and shape of the blocks used are in proportion

to the strength of the stone. The mortar, too, used for this purpose should be of the very first quality, and the stones accurately dressed. If the dressing is badly done, and the pressure is unequal and severe, they are liable to fracture. Some classes of stone can safely be employed for machine foundation in blocks of almost any size, but in others the sizes of the blocks should be proportional. A safe rule is to make the length of the block, say, about three times the thickness, and the width one and a half times; blocks of long dimensions in proportion to their thickness should never be used, as with heavy machines with a reciprocating motion, with a positive stroke or dead blow, the risk of breakage is considerable. Care must be taken that the masonry is accurately levelled, and set as near perpendicular to the direction of the stress or pressure as possible. The top blocks of stone should be cramped together, and the joints filled in with molten lead. The horizontal mortar joints should be from to inch in thickness, and the vertical joints about inch. These various precautions may appear to some to be slightly unnecessary, but, as excessive vibration and stress is in a great measure overcome by the weight and solidity of the foundation, the framing of the machine being as far as possible combined with and, so to speak, made integral with the foundation, this can hardly be so. The quality of the work turned out and the longevity of the machine depend also more on the stability of the foundations than is generally imagined. The foundation bolts should be of strong section, and the plates of ample area. The bolts should pass entirely through the masonry, and we have found there is less liability to fracture or work loose by any sudden strain by inter