All About Engines

James Watt: The Man and his Work 49 condenser opened and the piston was pressed down by the force of the steam into the vacuum created by the condenser. The valves were opened and closed by rods from the beam as in the Newcomen engine. The arrangement in this and all Watt engines is very difficult to explain, even with a Fig. 17.—Watt’s early cylinder Fig. 18.-Watt’s later cylinder drawing, and as it is now no longer used its considera- tion may be omitted. The cylinder described had certain disadvantages, and was replaced by the form shown in Fig. 18. In this the steam jacket was fed independently of the cylinder, as it is in engines to-day, and a port was constructed leading from the steam supply pipe into the space above the piston. The mode of opera- tion was similar to that in the earlier one. Steam first acted on the upper side of the piston ; then