CATALOGUE OF THE MECHANICAL ENGINEERING COLLECTION. 



31 



revolution farthest from the abutment and draws it out far enough 

 to pass the abutment previous to its arrival, and in, after passing. 



Steam and exhaust passages are led to the cylinder through the 

 sleeve inclosing the main shaft. Cat. No. 251,294 U.S.N.M. 



AIR AND INTERNAL COMBUSTION ENGINES. 



The expansion of air upon being heated and its contraction on 

 cooling has attracted the attention of many persons during the past 



FIG. 10. PLATT ROTARY KNGIXE, 1862. 



one hundred years, and has led to the invention of a variety of hot- 

 air engines. The earliest of these having real merit was patented 

 in England in 1827 by Dr. R. Stirling. The engine consisted of 

 two chambers filled with air and connected by pipes with each end 

 of a cylinder whose piston received a reciprocating action by the 

 alternate expansion and contraction of the air. In addition tlie 

 engine was equipped with a regenerator which absorbed some of the 

 heat of the air as it passed out of the cylinder and gave it out to the 

 incoming air. In later improvements made by Stirling the air was 

 compressed before heating, and an engine was designed so that the 

 same air could be used over and over again. This attempt at mak- 

 ing a theoretically perfect engine was more economical in fuel con- 

 sumption than any double-acting steam engine of that time, but the 



