DOMESTIC MOTORS. 



329 



Fig. 8. 



and the fire continues to burn, the water in the coil will be forced back 

 into the air-chamber, and the production of steam will cease. 



When the water is exhausted, the engine simply stops until the 

 supply is renewed. At the right of the pump a relief -valve is placed 

 to limit the pressure. It is not a safety-valve, as, even if it were ab- 

 sent, an explosion could not occur, as the mechanism of the pump is 

 not strong enough to produce a bursting pressure. The construction of 

 the generator is more fully shown in Fig. 7. It consists of a cylindri- 

 cal shell in which is coiled about thirty-five feet of seamless copper 

 tubincr. In the base of this is a gas-burner, L, and around it is a second 

 shell, leaving an annular space for the entrance of air. The air is also 

 admitted through openings at the bottom of the shell. The burning 

 gases pass up through the center of the 

 coils and down between the two, and 

 out by the draught-pipe. The exhaust 

 steam is discharged through the regen- 

 erator, where it partly heats the water in 

 the coil, into this draught-pipe. On first 

 lighting the gas, the cap A' is removed 

 and the flame allowed to burn up into 

 the air, but as soon as the formation 

 of steam begins the cap is replaced, and 

 the exhaust steam then creates sufficient 

 draught to carry the burning gases 

 through the coils into the draught-pipe. 

 The generator has but one fiftieth the 

 cubical capacity of that required by 

 an ordinary boiler to run the same en- 

 gine. The engine is of the simple os- 

 cillating type, and the whole apparatus 

 is attached to a bed-plate forming the 

 top of a vase-shaped receptacle. Fig. 

 8 shows the appearance of the com- 

 plete motor. In another form the vase 

 is supported by a bracket attached to 

 the wall instead of by the tripod. The 

 vase is used to hold the water from 

 which the pump supplies the reservoir. 

 Four or five quarts of water once in as 

 many hours is generally sufficient in the 

 ordinary use of the machine. 



The engine in this size is far from 

 being economical, requiring twelve cu- 

 bic feet of gas an hour, while it only 



furnishes a thirty-third of a horse-power. Efficiency, however, is not 

 very important with such a small motor. This amount of fuel, with 



