DOMESTIC MOTORS. 325 



and can be used anywhere in a house without annoyance, as they run 

 with almost no noise. They occupy but small space, the boiler-casing 

 being in the smallest size but sixteen inches in diameter and three feet 

 in height. The base of the machine has air-spaces to prevent the heat 

 from burning the floor. The construction and operation of the pump- 

 ing-engine will be clear from an inspection of the cut. The heater B 

 surrounds the boiler C C, which is made with pendent water-tubes G G, 

 among which the burning gases circulate on their way to the smoke- 

 stack. The gas burns from a double argand burner II, the supply being 

 automatically controlled by the steam-pressure in an ingenious man- 

 ner. At I, a valve is placed in the gas-pipe which is operated by 

 the lever I, the longer end of which is pressed up by the spring M. 

 A tube, o, leads from the boiler to a chamber in which works the 

 diaphragm-piston r, attached to the shorter end of the lever L. If 

 the pressure in the boiler increases, it is transmitted to the piston 

 which rises and partially closes the valve I, diminishing the supply of 

 gas. A lessening of the boiler-pressure produces the reverse effect of 

 increasing the gas-supply. The amount of fuel consumed is thus ac- 

 curately proportioned to the amount of steam generated by the engine 

 itself. This allows the gas to be kept burning while no work is being 

 done, and consequently no steam used without there being the slight- 

 est danger of an explosion, a feature of gi'eat value in a power-engine 

 when it is used intermittently, but needs to be in constant readiness. 

 In the larger sizes in which coal is used, the fire is regulated by means 

 of an automatic damper operated in a similar manner to the valve 

 controlling the gas-supply. 



The feeding of water to the boiler is also controlled by a very sim- 

 ple automatic arrangement. The feed-water chamber is placed at the 

 top of the heater-shell, where it is exposed to the heat of the issuing 

 products of combustion. A pipe, h, is open to both the pump and this 

 chamber. So long as the feed-water heater is but partially filled, wa- 

 ter continues to be forced into it by the pump ; but, when it becomes 

 full, no more can enter until a portion of it has passed into the boiler. 

 The admittance to this latter is controlled by a float mechanism, E, F, 

 D, operating a valve at the base of the boiler through the medium of 

 the rod o. The float E is a flat, inverted vessel, which is partially sub- 

 merged when the boiler is full. A weight, D, at the other extremity 

 of the lever F, is then able to keep the valve closed ; but, as the level 

 of the water sinks, the float drops and the valve is opened by the rod 

 o, the pi-essure produced hy the pump forcing water from the feed- 

 heater into the boiler. By these two devices, the one controlling the 

 heat by the steam-pressure so as to keep that pressure constant, and 

 the other regulating the amount of water in the boiler, this steam- 

 engine becomes nearly as safe, and gives as little trouble, as any of the 

 simpler forms of heat-engine using hot air or gas. For still further 

 security a safety-valve is placed in the pipe leading from the boiler, 



