THE CONQUEST OF NATURE 



crank-shaft; the ignition spark leaped across the space 

 between two wires carried about ont-gkth of an inch 

 apart in a porcelain holder." 



In 1865 Mons. P. Hugon patented an engine similar 

 to that of Lenoir, except that ignition was accomplished 

 by an external flame instead of by electricity. The 

 ignition flame was carried to and fro in a cavity inside 

 a slide valve, moved by a cam so as to get a rapid cut-off, 

 and permanent lights were maintained at the ends of the 

 valve to re-light the flame-ports after each explosion. 

 The gas was supplied to the cylinder by rubber bellows, 

 worked by an eccentric on the crank-shaft. This en- 

 gine could be operated satisfactorily, except as to cost, 

 but the heavy gas consumption made it uneconomical. 



An important improvement in this regard was intro- 

 duced by the Germans, Herrn. E. Langen and N. A. 

 Otto, who under patents bearing date of 1866 introduced 

 a so-called "free" piston arrangement that is to say 

 an arrangement by which the piston depends for its ac- 

 tion partly upon the momentum of a fly-wheel. This 

 principle had been proposed for a gas engine as early 

 as 1857, but the first machine to demonstrate its feasibil- 

 ity was that of Langen and Otto. Their engine greatly 

 decreased the gas consumption and hence came to be 

 regarded as the first commercially successful gas engine. 

 It was, however, noisy and limited to small sizes. The 

 cycle of operations of an engine of this type is de- 

 scribed as follows: 



"(a) The piston is lifted about one-tenth of its travel 

 by the momentum of the fly-wheel, thus drawing in a 

 charge of gas and air. 



