DOMESTIC MOTORS. 



485 



In this country the engine is made for the trade in three sizes, from 

 two to seven horse-power, but those of larger power are built when 

 desired. The English makers furnish it from one up to forty horse, 

 and as wide a range is given it on the Continent. The engine, as shown 

 in the engraving (Fig. 12), is of the form constructed by the American 

 makers. The cylinder is placed horizontal and overhangs the substan- 

 tial bed-block of the machine. It is open to the atmosphere at the end 

 toward the fly-wheel, and is closed at the other by a head-piece in 

 which are the appliances for introducing and igniting the gaseous mix- 

 ture, the construction of which is shown in the sectional cut Fig. 13. 

 The head-plate A closes the cylinder entirely except at I, where there 

 is a passage for the admission of the combustible charge. Between this 

 plate and an outer one, C, is a slide-valve, B. The outer plate is 

 pressed against the valve by the spiral springs shown in Fig. 12. The 



Fio. 13. 



pipe supplying the gas opens in its inner face at c, and at m there is a 

 small jet constantly lit while the engine is in operation. The slide-valve 

 B has two channels, i and n, the former placing the air and gas in 

 communication with the cylinder, and the latter serving to ignite the 

 mixture. The piston being at the beginning of its stroke, the valve B 

 is in such a position that the air-inlet a and the gas-inlet c are in com- 

 munication with the passage I through the port i. The piston then moves 

 outward, drawing in a charge of air and gas which it compresses on 

 its return, the valve B having moved so as to close the opening I. By 

 this movement the channel n becomes filled with gas from the small 

 supply-pipe 0, which is ignited at the jet m. Just as the piston has 

 completed the compression of the gaseous mixture, n arrives opposite I 

 and ignites it, the valve continuing its motion so as to close the open- 

 ing. The piston is driven outward by the expansion of the gases, and 

 on its return they are expelled through the valve q in the side of the 

 cylinder operated by the mechanism of the engine. The slide valve is 

 reciprocated by a crank on the end of the lay-shaft, shown running 

 lengthwise of the cylinder, which revolves but half as fast as the main 

 shaft. The combustible mixture can therefore be drawn in only once 



