combustion chamber at the rear of the boiler, and returns through the smaller tubes to the

smoke bonnet, at the front end of the boiler, thence into the funnel, thus giving the greatest possible economy in the use of fuel.

are, at all times, below the water line.

The tubes

THE ENGINE. Figs. 70, 71, 72.

The cylinder and frame, and what is usually called the bed-plate, form one casting, the frame forming a hollow column with suitable openings for access to the moving parts.

The piston is conical in form, thus insuring a maximum of strength with a minimum of

material. The cross-head is of bronze, with the piston rod threaded into it and secured by a jamnut. The connecting-rod is rectangular in cross section, having a solid end at the cross-head, and brass boxes fitted with a wedge for taking up the lost motion. The crank-pin end of the rod is provided with the usual strap and key. All the journals are of ample size, thus insuring cool running even under severe conditions.

The link motion is of the Stephenson type, and is designed so as to produce an equal cut-off for all points of the stroke. All the small parts, as far as practicable, are of steel, as light as is consistent with required strength.

The crank-shaft is of steel, the crank-arms being fitted with counterbalances eccentrically bored to fit crank-discs, and firmly held by bolts. The after journal forms the driving bearing, the thrust of the screw propeller being taken by four steel rings, solid with and projecting from the shaft, providing ample surface, and insuring freedom from lateral action.

In ordinary operation, these engines are run at a speed of 300 revolutions per minute, with the steam cut-off at half stroke. At this speed there is little vibration, the weight of the reciprocating parts being accurately counterbalanced.

Any lateral movement of the cylinder is largely avoided by the suspended position of the shaft. The centrifugal action of the counter

balance, which is a trifle greater at midstroke than that of the connecting-rod, has a tendency to impart a lateral movement to to the shaft. This action has been carefully considered, and the foundation timbers so located as to resist this tendency.

The "Acme" launch engine shows the smallest size marine engine. It is 3 inch bore, 4 inch stroke, and will develop, if required, about four

indicated horse-power. The crank-shaft, pistonrod, valve-stem and pins are made of steel as well as the link. It is a very quick, powerful little engine. Its weight is 145 pounds, and its height is 30 inches to the top of cylinder.

Fig. 74 shows the style of engine which they call the "Peerless" engine. The arrangement of the link is such as to dispense with five or more moving parts, and have the link-block take up its own wear, thus avoiding any rattle at this point.

The Peerless marine engines are among the simplest, most compact and strongest in the market. The crank, connecting-rod, piston-rod and stem, and pins, are made of steel. The iron frame of the engine and the slides, as well as the bearing for the crank-shaft, are made in one piece, so that it is impossible for the working parts of the engine to get out of line or change their relation to each other. The construction of the engine is such that the action of the piston-rod is exactly central, and all overhanging strains are avoided.

The engines that are fitted in launches are what is known as the inverted-cylinder, highpressure type of engines. They are very simple in construction, not liable to derangement, and with ordinary good usage should run for ten years without any extensive repairs. They have large bearing surfaces, are fitted with steel reversing links, and provision is made for perfect lubrication. All the wearing parts are easy of access, and are adjustable to wear. They are short stroke, quick, powerful little engines, and are very economical of steam.