Steam enters the vertical stem by means of a pipe, and as it rushes up and out through the lateral tubes D, it strikes the angles E at the discharge ends, so that an impulse is given which drives the ends of the tube in opposite directions. As the fluid emerges from the ends of the tubes, it expands, and on contacting with the air, the latter, to a certain extent, resists the expansion, and this reacts on the tube. Thus, both forces, namely, impact and reaction, serve to give a turning motion to the turbine.
The Reciprocating Engine.—The invention of this type of engine is wrapped in mystery. It has been attributed to several. The English maintain that it was the invention of the Marquis of Worcester, who published an account of such an engine about 1650. The French claim is that Papin discovered and applied the principle before the year 1680.
In fact, the first actual working steam engine was invented and constructed by an Englishman, Captain Savery, who obtained a patent for it in 1698. This engine was so constructed as to raise water by the expansion and condensation of steam, and most engines of early times were devoted solely to the task of raising water, or were employed in mines.
Atmospheric Engines.—When we examine them it is difficult to see how we can designate them as steam engines. The steam did not do the actual work, but a vacuum was depended on for the energy developed by the atmospheric pressure.
A diagram is given, [Fig. 10], showing how engines of this character were made and operated. A working beam A was mounted on a standard B, and one end had a chain C on which was placed heavy weights D. Near this end was also attached the upper end of a rod E, which extended down to a pump.
