should then be embedded in the cement. Such a method is shown in section in Fig. 119.

Mufflers and exhausts on stationary engines should be well covered or protected with asbestos, for they become very hot and are liable to cause bad burns or even set fire to some object that happens to come in contact with them. Exhaust pipes, where led through a wooden wall or partition, should be protected, and a metal collar should be used over the hole with a space of at least one inch between the pipe and the nearest wood. The outer end of the exhaust should be led away from all surrounding objects or walls and should never lead into a chimney, water or steam pipe, smokestack, or other confined space. If this is done unburnt charges of gas may enter and later explode by flame or heat with serious results. If a wooden bed is used it should be firmly mortised or bolted together and should be securely fastened to the flooring or ground. Many engines are given far too light a bed, and when under full power will jump and vibrate tremendously. A good bed should be strong and steady enough to hold the motor down immovably under its highest speed and greatest load.

When installing a marine engine the method is governed to a great extent by the boat, the timbers, and the accessibility of the location. Timbers for a boat engine's bed should be of well-seasoned hardwood of ample size and strength, and should be securely bolted to ribs and keel, but not to the planking. A very good plan is to use two long timbers running lengthwise, or fore and aft, of the boat and fastened to the ribs. Across these the

bed timbers should be bolted and these should also be securely fastened to the keel. In a flat-bottomed boat timbers may be set across the boat, bolted to keel and sides, and the engine-bed bolted lengthwise of these (Fig. 120). This method takes the jar and vibration from the floor boards and planks. Great care should

Fig. 120. Engine Beds in Boats

be taken in getting a marine engine level and in absolute line with the shaft; a very slight deviation will cause enough friction on the shaft to stop the engine or hold it down to only a fraction of its speed and power. I have seen a ten-horse-power motor that could not be turned over more than one explosion owing to a bend in the shaft so slight as to be scarcely perceptible to the eye.

Where it is difficult or impossible to get a perfect alignment, or where there is a constant vibration or motion, the shaft should be connected through a universal joint. Flexible unions, elbows, joints, and stuffing boxes may also be used if desired. In vehicle construction with a shaft drive universal joints cannot well be avoided, and in many high-powered and racing boats they are also used to great extent; but it is better to avoid flexible connections as far as possible, as they are expensive, cumbersome, and must be given considerable care if they are to prove efficient.

The exhaust piping in a boat can be so readily cooled by admitting a part of the circulating water that there is no excuse for its ever burning or scorching anything, but nevertheless it is a good plan to have it well protected and led in such a way that it will not be in the way of people passing to and fro. A marine motor, more than any other, should be handy and accessible and ample room should be left on all sides to allow it to be adjusted, taken apart, or cleaned readily, and the drain cock in base should be within easy reach. It is usually most convenient to have the exhaust on the port and the intake on the starboard side where the operator sits behind the motor, but the arrangement of such matters must be guided by the conditions in each particular case. In installing any engine the exhaust silencer should be as near the motor as possible, and the exhaust pipe should be as short and with as few bends and turns as can be arranged. Where right angles must be made in an exhaust pipe two forty-five-degree elbows should be used instead of one common elbow, and tees

should be avoided as much as possible; they always have pockets which are a nuisance. Connections as far as possible should be made with flanges or flanged unions, as ordinary screw unions and right-and-left couplings soon become so foul and corroded as to be impossible to disconnect. The exhaust in a boat should always be so arranged as to slant downward from the motor to

the outlet, for even if far above the water line a wave may now and then wash into the exhaust.

If a long exhaust pipe is unavoidable it should be gradually increased in size, and it is a good practice to always use a larger-sized pipe at every turn of the exhaust pipe beyond the first. For connecting up an exhaust pipe lead and oil should never be used, as it soon burns out and either leaves a leaky joint or cements

the joints together into a solid mass. Cylinder oil and graphite make an excellent joint, and even linseed oil and graphite is very good. Where a solid and permanent job is desired the joints may be made with red lead and molasses, or with litharge and glycerine, or with a cement composed of sulphur, iron filings, and sal-ammoniac mixed into a thin paste with water. Well-fitting threads may also be well cemented together by the use of salammoniac and water alone. Where the boat is intended

Fig. 122.-Installation of Exhaust above Water-line

for salt-water use the exhaust pipe should be of galvanized iron, and this is far better than black iron even where used around fresh water or for stationary motors. A sample of a well-installed marine exhaust is shown in Fig. 121. This illustrates an under-water exhaust, while Fig. 122 shows methods of exhaust piping when above the water line. In Fig. 123 is shown the method of properly piping a stationary exhaust where it was carried a long distance and several turns had to be made.

The water-circulation pipe connections should be made with care, for a small air leak in the intake will often cause failure of the pump, and a leak in the outlet