a nuisance, which sounds harshly not only to the engineer, but to all who have an ear for natural mechanics. Nothing, perhaps, makes the intelligent engineer feel so cheap as to be found in charge of an engine that knocks, as lookers-on are not always capable of deciding who is at fault-the engine or the engineer. The Remedies for Knocking in Steam-Engines. While it may be possible in most cases to locate the knocking in steam-engines, and explain the causes from which they arise, it is hardly possible to prescribe a remedy for all, as, in many instances, it must arise out of and be determined by the circumstances of the individual case. The most practical method of remedying the knocking induced by the crank-pin being out of line, is to place the crank-shaft at right angles with the centre of the cylinder, remove the old crank-pin, rebore the hole so as to bring the centre of the new pin perfectly in line with the axis of the cylinder, and replace the old pin with a new one. The knocking induced by the wrist-pin and crank-pin becoming worn oval, may be remedied by filing them perfectly round; but the knocking caused by the crank-shaft journal being worn out of round is very difficult to remedy; in fact, there is hardly any remedy for it, except to remove the shaft, true it up in a lathe, and refit the boxes, which operation is attended with a good deal of difficulty, more especially when the engine is large. Knocking in the boxes on the crank-pin and cross-head, or valve-rod, may be remedied by filing out the boxes and readjusting the keys, or by putting a liner behind or in front of the boxes, when there is not sufficient draught in the keys and gibs. Knocking in the steam-chest caused by looseness in the valve connections may be remedied by readjusting the jam-nuts or the yoke. Knocking arising from this cause manifests itself more frequently when steam is shut off from the cylinder, preparatory to stopping the engine, than when the engine is running; the lost motion is taken up in the valve connections by the pressure of the steam on the back of the valve. Knocking in the piston is generally caused by the rod becoming loose in the head, and, if it continues for any length of time, it destroys the fit of the rod in the hole. The only practical remedy under such circumstances is to remove the rod, rebore the hole, and bush it or thicken the rod at that point by welding, and fit it to the head after the hole is rebored perfectly true. Knocking in the follower-plate is generally caused by the bolts being too long, or from dirt being allowed to accumulate in the holes, which prevents them from entering sufficiently far to take up the lost motion in the plate, and may be remedied by shortening the followerbolts, or removing the deposits from the bottoms of the holes, as the case may be. The knocking caused by shoulders becoming worn in the cylinder at each end can be remedied by reboring the cylinder, and making the counter-bore sufficiently deep that a part of one of the rings will overlap it at each end of the stroke. Knocking caused by shoulders becoming worn on the guides can be remedied by planing the guides and making the gibs or shoes sufficiently long that they will overrun the guides when the crank is at either centre. The knocking induced by any of the foregoing causes is generally a source of great annoyance to the engineer, as any attempt to adjust the boxes on the cross-head or crank-pin, or the piston-packing in the cylinder, generally aggravates the cause of the knocking, as any adjustment of the connecting-rod boxes alters the position of the piston in the eylinder and the cross-head on the guides, and causes them to strike harder against the shoulders. Knocking caused by the valve or valves being improperly set may be remedied by removing the bonnet of the steam-chest and adjusting the valve, so that it may move uniformly on its seat, thereby giving the same amount of lead at each end of the stroke; then, if the valve is well proportioned, and the connections thoroughly fitted and skilfully adjusted there is no reason why the engine should knock from this cause. But the knocks arising from bad proportion in the valve or steam passages are the most difficult of all to remedy, as they are inherent in the machine. The Douglas Automatic Cut-Off Engine. The cuts on pages 157, 158, represent the Douglas Automatic Cut-Off Engine. It will be noticed that the bed-plate is of the girder-frame pattern, which is faced up to receive the cylinder at one end and the main pillow-block bearing at the other. The cylinder rests on a tapering pedestal, while the back end of the bed-plate and crank-shaft bearing is supported by a double leg, which is cast solid with the bed-plate. The pillow-blocks at the cylinder-base are placed on the under side, and are situated at equal distances from the centre, which facilitates the setting up of the engine or placing it in line, as all that is necessary is to level the foundation stone and place the engine on it. The cross-head guides are bored out cylindrical, and on line with the centre of the cylinder, which obviates the liability of the engine getting out of line. The main steam-valve serves both for induction and exhaust.' The exhaust passes through its centre to the exhaust-port at the centre of the cylinder. It receives its motion from an eccentric, through the intervention of a rocker-arm and small take-up connections from the rocker-arm to the valve-rod. The two cut-off valves are flat, and slide on the top of the main valve. They receive their motion from an extra eccentric and rocker-arm. On this rocker-arm is a disc, pivoted on its centre. At equal distances from the pivot-pin, in opposite directions, are two wrist-pins, to which the cut-off valve on the frame end is attached by a take-up connection and spade-handle joints to the lower pin of the disc, while the steel rod passing through the sleeve to move the other cut-off valve is attached to the other pin on the disc. The lever and connection attachments from the governor to the rocker and disc rotate either way, separating the cut-off valves or drawing them nearer together, cutting off the steam earlier or later in the stroke, to accommodate a varying load and pressure. The governor is very powerful, sensitive, and positive in its action, and can be driven by either belt or gearing. Should the belt |