TESTING THE VALVES.
An experienced engineer will most easily determine the existence of leaks between the valves and their seats when the engine is working, and the indications of that weakness have already been noticed. But it sometimes happens that a man wishes to test the condition of the valves when the engine is at rest. This can be most readily accomplished by placing the engine so that the rocker-arm stands in the vertical position. Open the smoke-box door so that the exhaust nozzles can be seen. Now block the wheels, and give the engine steam. If the valve blows, the steam will be seen issuing from the nozzle on the side under examination. As the tendency of a slide-valve is to wear the seat concave, it sometimes happens that a valve is tight on the center, yet leaky in other positions. Moving the valve with the reverse-lever as far as can be done without opening the steam-port, will sometimes demonstrate this. The cranks should be placed on the eighths positions when the valves are being tested.