DOMESTIC MOTORS. 483 



DOMESTIC MOTOES. 



By CHARLES M. LUNGREN. 

 III. GAS AND ELECTRIC ENGINES. 



THE gas-engine differs from both the steam and hot-air engine in 

 the character of the expansion of the elastic fluid employed and 

 in the mode of applying the heat. In the one the fire is used to con- 

 vert water placed in a vessel exterior to the engine into steam, which, 

 let into the cylinder, moves the piston by its expansive force ; and in 

 the other it is used to expand a volume of air contained in the cylinder 

 or adjacent chamber. 



In both, the heat is applied outside of the working cylinder, but 

 the peculiarity of the gas-engine is that the heat is developed within 

 the cylinder itself. A mixture of gas and air is by the operation of 

 the engine drawn into the cylinder, and then exploded, the heat gen- 

 erated expanding the products of combustion, which, exerting a pres- 

 sure against the piston, give it motion. Simple as is this mode of 

 converting heat into work, the practical realization of it has been 

 found to be exceedingly difficult, and it is only within a very few 

 years that thoroughly serviceable machines have been constructed. 

 The most economical result is obtained from expanding gases when 

 the pressure they exert is a continuous and gradually diminishing 

 one, such as that of steam in the steam-engine. With an explosive 

 mixture, like that in the gas-engine, the expansion takes place with 

 great rapidity, producing a sudden and unsustained pressure, from 

 which it is difficult to get either an economical result or a steady 

 operation of the mechanism. This rapidity of expansion can be de- 

 creased, and the pressure obtained approximated to that of the steam- 

 engine, by altering the proportions of air and gas so as to produce a 

 quick combustion instead of an explosion, and by introducing the 

 gaseous mixture into the cylinder gradually, instead of all at once ; 

 and it is in this direction that the improvements have taken place 

 which make the latest forms of gas-engine so superior to their prede- 

 cessors. 



Among the first engines to obtain a moderate degree of success 

 were those of Hugon (1858) and Lenoir (1860). Neither of these 

 was, however, very economical in the use of gas, and, previous to the 

 engine of Otto and Langen in 1867, none were produced that were at 

 all satisfactory in this respect. This was, however, objectionable, owing 

 to the intolerable din it made when in operation. 



While this engine was at best but a very qualified success, it has 

 led the way to a machine which is very far from being so. In the 

 Otto silent gas-engine, introduced a few years since, and now made 



