EXPLANATION OF THE PLATES. 329 



PLATE II. 



This plate represents a plan and two sections of a cylindrical steam boiler, 

 (art. 227 230.) Fig. 1. is a cross section, Fig. 2. a longitudinal section, and 

 Fig. 3. the plan ; in the last, half of it is the plan above the level of the boiler 

 bottom, and the other half below it. The fuel is put in at the fire-door B, it 

 inflames at D, and the smoke in passing over the hot current of air rising through 

 the red fuel at E is consumed. The ash-pit door is supposed to be provided with a 

 register to regulate the admission of air, but it would be better to make it regulate 

 itself as in the preceding plate. By pushing back the plate k by the handle i, the 

 clinkers are let out behind, (art. 248.) The supply of water is regulated by a 

 hollow copper-ball float, and the supply is continuous, except, when by the water 

 rising, the valve is closed, (art. 254.) To prevent sediment depositing over the 

 fire, I would recommend a division to be placed across the boiler as at O ; the 

 safety pipe T W is recommended instead of the valve, on account of the certainty 

 of its action. The first effect of strong steam is to displace the water down to the 

 level of the mouth of the pipe at T ; this sets the feed pipe into action, and steam 

 and water rise by the pipe T W till the boiler be cooled to its proper temperature, 

 (art. 264 ;) no internal valve is required : S is the steam pipe leading to the 

 engine. The same letters refer to the same parts in all the figures. For the area 

 of the grate, and ash-pit, see art. 197 199; size of the boiler, art. 229; the 

 area of the chimney, art. 274 278 ; and the strength of the boiler, art. 525. 



Note. In Section III. I neglected to remark that the boilers formed of small 

 pipes cannot possibly produce more effect than others, and that every boiler must 

 contain a certain quantity of water and steam, otherwise the slightest neglect of the 

 fire would cause the engine to stop. It has been pretty clearly ascertained that not 

 one of the combinations hitherto proposed, has equalled the kind of boiler above 

 described. 



