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Rh by the piston when exhausting, it should be understood that the exhaust port is closed just before the piston reaches the end of each stroke, so that a small quantity of steam is what is called 'trapped' in the cylinder. This serves as a cushion, and prevents the reversal of the direction of the piston being accompanied by any shock. We do not go into the mysteries of 'lap and lead,' as they are matters which the manufacturers of steam engines satisfactorily settled long ago, and the automobilist need not trouble himself concerning them.

Anyone who is absolutely unacquainted with link motion and steam engines generally should, if he wishes to get an insight into the working of an engine, spend a quarter of an hour examining a small model steam engine. He will learn more of its working—which is very simple in itself, though laborious to plainly describe—in five minutes than he can from as many hours of reading. It should be understood, with regard to figs. 23, 24, and 25, that the link motion is shown at right angles to its true position, as, while we have an end view of the cylinders and slide valve, we have a side view of the links and eccentric rods, this distortion occurring merely for the sake of clearness. Nor are the eccentrics fixed quite at right angles to the crank, but to explain this would occupy more space than we have at our command.

The Reading Engine.—Nearly all the small steam cars are driven by two-cylinder engines, the only exception being the Reading, in which a four-cylinder engine is used. This is a most ingenious engine, which we regret space does not permit us to describe in detail. It has no slide valves, and the steam is admitted to and released from each cylinder by a single rotary valve, this one valve on the top of the four cylinders serving them all, and also providing for reversing. This engine was fully described in 'The Autocar' of April 20th, 1901, and September 21st, 1901.

Compound Engines.—The engine driving the House car is a two-cylinder one, but it is so arranged that one cylinder receives high-pressure steam from the boiler, and, instead of