Chemical and Physical Papers. 51 



steam as it flows from a state of high to a lower temperature. 

 The turbine is also combined with the reciprocating engine, 

 each forming a stage in a compound unit. In this way the 

 turbine is enabled to get as much power out of a pound of 

 steam after it has expanded to a pressure at which it would 

 be thrown away in a noncondensing plant as the noncondensing 

 steam engine would get out of that pound of steam above that 

 pressure, thus adding a large percentage to the efficiency of 

 the plant. 



With every new invention in power machinery comes the 

 statement that the steam engine is doomed and about to be 

 relegated to the museum as a curiosity. This happened when 

 the steam turbine came into use, and it is happening again 

 with the advent of the Diesel motor ; but that the steam engine 

 has managed to hold its own is evidenced by the fact that of 

 the total horsepower produced in the United States, after 

 fifteen years of the steam turbine and gas engine, 75 per cent 

 or more is by the reciprocating steam engine. Not only has it 

 held its own as a mechanical device, but its thermal efficiency 

 has been increased to keep pace with improvements in other 

 lines. Speaking roughly, we may say that the efficiency of the 

 steam engine has been practically doubled, both for small and 

 large units, in the last decade. The agencies that have brought 

 this about are the invention of the German uniflow engine, 

 which has an ordinary efficiency about equal to the best mul- 

 tiple-expansion engine working under the most favorable con- 

 ditions ; the locomobile, a combined engine and boiler which 

 will give an efficiency for small plants about as good as the 

 best multiple-expansion engine under the most favorable con- 

 ditions ; the elimination of smoke and consequent saving of 

 fuel; the superheating of steam, which saves the losses from 

 condensation and reevaporation. 



The development in the production of gas power has been 

 mainly in the direction of reliability. In this period gas 

 engines have been perfected to the point where they will 

 f^tart, and riin after they get started. With the perfection in 

 details has come an increase in the size of the units, so that 

 whereas fifteen years ago a gas engine of over 40 horsepower 

 was the exception, we now find them running successfully in 

 units of several hundred horsepower. 



The gas-producer plant has shown less development, perhaps. 



