friction and wear due to the weight of the shaft, which prevents heating and the liability to get out of line. The following shows the relief afforded in an engine of medium power. For example, take an 18x36 with an initial pressure of 100 pounds. Main bearings are relieved of 17 tons of steam pressure at each stroke of the pistons, and also the thrust of the rods, at a velocity of 500 per minute, gives a total relief of 21 tons per stroke. It will readily be seen that the greater the power required the more important it is to obtain a balance. It will also be seen, by perfectly balancing the moving parts, as is done in this case, no power is lost in lifting the weight or forcing up the pistons. And for the same reason uniformity of motion is obtained, insuring great durability. Another very important feature of the principle is that the hull of the vessel is relieved of all strains (from the force applied) excepting the pressure from the screw. Quadrupled for high steam pressure, this engine occupies one-third less space than the ordinary triple. The important advantages to be derived by using steam upon the balance principle is practically unknown, for the reason that heretofore no engine has been constructed to obtain a balance that did not embrace grave mechanical objections. Hence there was no means of putting it to practical test, until this design was put in use. The principle demonstrates in

practice an important gain in power, great durability, uniformity of motion, and the absence of all vibration.

MODERN HIGH SPEED YACHT ENGINES.

The increasing interest now taken in steam yachting has necessitated a better class of machinery than heretofore. Speed is now of the first importance, though most owners are particular about the appearance of their engines and wish them to be as attractive as possible. Fig. 80 represents a triple expansion engine built by John W. Sullivan, New York, and is a fair example of the high grade of work turned out by this shop. The cylinders are all three in one casting so as to save weight, the back of columns, which carry the guides for the crossheads, are all cast hollow of steel, and the bed plate is also of steel for the same reason. Piston valves are used throughout driven by Bremme gear, so that the engine is very open in appearance, easy of access and greatly simplified. Light steel columns support the front of the cylinders, which being polished add greatly to the appearance of the engine. The crank shaft and eccentrics are forged steel in one piece, while the connecting and piston rods, valve gear and all bolts and nuts, are also steel. The connecting rods are bored through the centre in order to further reduce the weight. The air and two feed pumps