THE CONQUEST OF NATURE 



wasteful method of securing rotary motion indirectly 

 through the aid of pump and water wheel. It may be 

 added, that the centrifugal governor, with which 

 modern engines are provided to regulate their speed, 

 was the invention of Watt himself. 



FINAL IMPROVEMENTS AND MISSED OPPORTUNITIES 



In the year 1782 Watt took out patents which con- 

 tained specifications for the two additional improve- 

 ments that constituted his final contribution to the pro- 

 duction of the steam engine. The first of these provided 

 for the connection of the cylinder chamber on each side 

 of the piston with the condenser, so that the engine be- 

 came double acting. The second introduced the very 

 important principle, from the standpoint of economy 

 in the use of steam of shutting off the supply of steam 

 from the cylinder while the piston has only partially 

 traversed its thrust, and allowing the remainder of the 

 thrust to be accomplished through the expansion of the 

 steam. The application of the first of these principles 

 obviously adds greatly to the efficiency of the engine, 

 and in practise it was found that the application of the 

 second principle produces a very great saving in steam, 

 and thus adds materially to the economical working of 

 the engine. 



All of Watt's engines continued to make use of the 

 walking beam attached to the piston for the trans- 

 mission of power; and engineers were very slow indeed 

 to recognize the fact that in many in fact in most- 

 cases this contrivance may advantageously be done away 



[102] 



