SECT, in.] CONDENSATION OF STEAM. 137 



254. The same construction applied to the feeding pipe of a low pressure 

 steam engine would be much superior to the common stone float; and I think 

 it would apply, as shown in Plate n. Fig. 2. even to the steam boat ; for the 

 oscillation would not prevent either its rise or fall, when an over-supply took 

 place or otherwise ; and employing the rise instead of the fall of the water to act 

 on the valve, would be a means of safety as well as of preventing irregular influxes 

 of water to check the steam. (See art. 217.) 



255. In a method of admitting water to high pressure boilers invented by 

 Mr. Franklins, the waste water has to raise a loaded valve to escape, and the 

 passage to the boiler is regulated by a balance float placed wholly within the 

 boiler : it is ingenious, but has not the advantage of rendering the supply con- 

 tinuous ; it must, as with the ordinary feed pipe, stop till the water has descended 

 so as to raise the valve. 



OF REGULATING THE FlRE OF A STEAM BoiLER. 



256. The force of the steam may be made a means of regulating the fire, 

 either by diminishing the supply of air, or by contracting the chimney by a plate 

 called the damper. As a means of regulation the former ought to be preferred ; 

 it being obvious, that a direct diminution of the quantity of oxygen at its entrance 

 to the fire must have both a more immediate and a more beneficial effect than 

 contracting the chimney ; the effect of the latter being to increase the tempera- 

 ture and force of the smoke in proportion as the aperture is contracted ; and, 

 consequently, the smoke escapes at a higher temperature, carrying off a consider- 

 able quantity of heat. The regulation by the damper is the kind generally used ; 

 the other method is the same in principle, and only differs in being applied to the 

 ash-pit instead of the flue. 



257. Self-regulating Dampers. Dampers are frequently under the control 

 of those who have the management of the fire ; but in the self-regulating damper 

 the fire is made a means of controlling itself, so as to burn with more or less 

 rapidity as it may be more or less wanted, in the following manner. An iron 

 plate or damper, of sufficient size entirely to close the chimney or flue, slides up 



which the water was required to be kept : notice of its evaporation below that point was given by 

 the steam forcing its way through the pipe, and producing a whistling noise, sufficiently loud to 

 call the attention of the engine tender, even if at some distance from his post. Subsequently, the 

 feeding and damper apparatus above described was applied to the Soho Mint engine, about the 

 year 1798 ; also to Retford cotton mills, near Nottingham, in 1803 ; and the same arrangement 

 continues to be much in use up to the present time. 



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