x PRACTICAL PURPOSE 261 



More than two thousand years ago, Heron of Alexandria, 

 who with Archimedes stands out from the Greek philo- 

 sophers of his day because of his mechanical ingenuity, 

 invented a kind of steam-engine in which the reactive 

 force of steam escaping from jets on a hollow metal ball 

 caused the ball to spin round. The principle of this 

 engine was similar to that of the steam-turbine which 

 has been developed so remarkably by Dr. de Laval and 

 the Hon. Sir Charles A. Parsons since 1880. Heron's 

 machine, however, was only a toy, and the first successful 

 engine put to practical use was invented by Captain 

 Savery in 1698. This engine was employed for pumping 

 water ; and the principle of its action is the same as 

 that of the modern pulsometer pumps now extensively 

 used. 



The beginning of the steam-engine as we now know 

 it, containing a cylinder into which steam enters, and 

 a piston moving in the cylinder, was the atmospheric 

 engine devised in 1705 by Thomas Newcomen, a black- 

 smith of Dartmouth, England. An overhead beam 

 capable of swinging up and down, like a see-saw, was 

 connected with a piston on one side and with a pump- 

 rod on the other. The piston could move up and 

 down in a cylinder connected to a boiler by a steam- 

 pipe furnished with a valve. When the piston was at 

 the top of the cylinder, steam was admitted, the valve 

 was closed, and a jet of water was caused to play into 

 the cylinder. The steam was thus condensed, leaving 

 a partial vacuum in the cylinder, with the result that 

 the piston was forced down by the pressure of the 

 atmosphere above it ; and as it pulled down one arm 

 of the overhanging beam, the other arm connected with 

 the pump-rod was pulled up. The weight of the pump- 

 rod would then pull down its end of the beam and the 



