CATALOG OF THE MECHANICAL COLLECTIONS 149 



To start the engine it was necessary to heat the water about the 

 retort to generate the vapor and to heat the igniter. When running 

 the engine developed sufficient heat for both purposes. 



Perry designed this engine so that the water served not only to 

 cool the cylinder but also to lubricate the piston and piston rod. 



ALFRED DRAKE GAS ENGINE, 1855 

 Plate 30, Figuee 2 



U.S.N.M. no. 308724; original patent model; transferred from the United States 

 Patent Office; photograph no. 18493D. 



This model was submitted with the application for Patent no. 

 12715, issued to Alfred Drake, of Philadelphia, Pa., April 17, 1855. 



As early as 1843 Alfred Drake exhibited a gas engine at Philadel- 

 phia. This one of 1855, however, is the only one that he patented. 

 The incandescent igniter is the novel feature of the engine. 



In this engine and the earlier one gas and air were drawn into th© 

 cylinder at atmospheric pressure, and the mixture was fired by a small 

 metal tube kept at white heat by an external flame. The force of the 

 explosion drove out the piston, giving a maximum pressure of about 

 100 pounds per square inch. The cylinder has a water jacket, and 

 the piston is hollow. 



The engine was afterward modified and worked chiefly by 

 petroleum. 



OTTO AND LANGEN GAS ENGINE, 1867 



Plate 31, Figtjke 1 



U.S.N.M. no. 308675; original patent model; transferred from the United States 

 Patent Office; photograph no. 10498. 



This model was submitted with the application for Patent no. 

 67659, issued August 13, 1867, to Nicolaus Otto and Eugen Langen, 

 of Cologne, Germany. 



This is the Otto and Langen free-piston or atmospheric gas engine 

 introduced at the Paris Exposition of 1866. In this design the in- 

 ventors improved the expansion of gases in the engine by employing a 

 free piston, which, in theory, gives unlimited expansion. 



In the model a long, slender, vertical cylinder, water-jacketed for 

 one-third of its lower end, is fitted with a short piston. The piston rod 

 is a toothed rack that is always engaged with a gear wheel at the top 

 of the cylinder. This gear runs free on the motor shaft during the 

 upstroke of the piston but is connected automatically to the shaft in 

 an ingenius roller clutch during the downstroke. A valve rod driven 

 by an eccentric on an auxiliary shaft operates a slide valve at the base 

 of the cylinder. Air and gas are drawn into the cylinder during the 

 upstroke. The mixture is exploded by a flame when the piston is 



