The valve gear on the gas compressing cylinder is arranged so that no gas is delivered to the inlet valves of the working cylinder until the air cylinder has provided sufficient air to insure perfect scavenging of the products of combustion, this preventing the fuel from becoming contaminated with the burnt gas. Speed regulation for varying loads is effected by shifting the valve gear of the gas pump so that the gas is delivered at an earlier or later period in the stroke of the working piston, thus causing a variation in the quantity of gas delivered to the working cylinder. This is controlled by the governor directly on the valve gear of the pump or upon a by-pass in the pump cylinder or both. The by-pass, when open returns all of the gas in the passage leading to the inlet valve, that is beyond a certain pressure to the cylinder, so that the gas is delivered to the cylinder at a constant pressure, and therefore in proportion to the load and point of cut off. This method of governing produces a mixture that varies in richness with the different loads that are carried by the engine, but as the air enters the cylinder first and is prevented from mixing to any extent with the gas by the shape of the cylinder heads, the igniting value of the mixture is not disturbed particularly as the rich gas remains in the cylinder heads and in contact with the igniters. Like all large engines, the Koerting is started by compressed air taken from a reservoir. A special starting valve is provided for each end of the cylinder which is operated from the cam shaft by means of an eccentric. The air valves may be thrown in or out of gear by a clutch. (57) Two Stroke Cycle Rail Motor Cars. A unique application of the two stroke cycle motor will be seen in Fig. 56 which shows a Fairbanks-Morse two stroke cycle motor direct connected to the driving wheel of a railway motor car. The three cylinders are mounted between the driving wheel with the ends of the axle terminating in the crank cases of the motors. Access to the bearings is had through a cover on the crank-case. The simplicity of this motor and its freedom from valves, cams, springs, gears, and other trouble causing parts makes it particularly adapted for the service that it performs in the hands of unskilled track laborers. As there is no water to freeze or leak, and as the lubricant is mixed with gasoline, the car needs very little more attention than the old type hand car.