Fire-places and Kitchen Utensils. 487 



The semi-circular tube d, which is represented filled 

 with water, serves to connect the two cylinders to- 

 gether. 



By the tube c, the water, which results from the con- 

 densation of the steam in the steam-tubes which warm 

 the room, returns to the reservoir which feeds the 

 boiler. This water, after falling into the cylinder a, 

 passes through the semi-circular tube d into the cyl- 

 inder b, and then goes off from that cylinder, and is 

 conveyed, still warm, to the reservoir, by the tube e. 



This simple apparatus serves as a safety-valve in the 

 following manner: When the steam in the steam-tubes 

 is redundant, it descends through the tube c, and 

 forcing the water out of the semi-circular tube d into 

 the cylinder b, it follows it through that tube, and, 

 escapes into the open air through the open end of that 

 cylinder. When the strength of the steam is suffi- 

 ciently diminished, a small quantity of water, still 

 remaining in the lower part of the cylinder b, returns 

 back into the tube d, and cuts off the communication 

 between the external air and the inside of the steam- 

 tubes. 



When, in consequence of the fire under the boiler 

 being extinguished or being much diminished, a vac- 

 uum begins to be formed in the steam-tubes, the 

 external air, pressing against the surface of the small 

 quantity of water remaining in the lower part of the 

 cylinder b, forces it through the semi-circular tube d 

 into the cylinder a, and following it into that cylinder 

 opens for itself a passage into the steam-tubes, and pre- 

 vents their being crushed by the pressure of the atmos- 

 phere, on the condensation of the steam. 



When the fire is gone out, and the whole apparatus 



