BOILERS AND PIPES. 



235 



excellent article, will show Mr Hood's 

 method of setting his arched boilers. 

 a is the furnace door ; b, ash-pit ; c, the 



Fig. 317. 



Fig. 319. 



Fig. 318. 



1 



nil II II 



1 







k 



















































/ 





1 





f 



















c 







dumb or carbonising plate ; d and e, small 

 iron doors, for the purpose of extracting 

 the soot from around 

 the boiler; — a corres- 

 ponding one on the 

 opposite side is not 

 shown, as the brick- 

 work is supposed to 

 be removed, to show 

 the side of the 

 boiler ; // are the 

 upper and lower flues 

 which pass round 

 the boiler, separated 

 by an iron flue-plate marked g; h, a brick 

 separation of the flue on top of the 

 boiler ; i and Tc, two fire-clay lumps, 

 placed close to the back of the boiler. 

 The space between them is from 3| to 4^ 

 inches, according to the size of the 

 boiler and height of the chimney. This 

 opening is the only passage for the flame 

 and smoke to pass through from the 

 furnace into the flues. We have no 

 doubt this latter contraction has a ten- 

 dency to retain the heat longer in the 

 oven of the furnace before it escapes into 

 the chimney, and is consequently lost. 



On the same subject we have the fol- 

 lowing remarks from Mr Ainger, in his 

 Essays On the Production, Distribution, 

 and Preservation of Heat, &c, published 

 in " The Gardeners' Chronicle :" — " In 

 the examples of boiler-setting usually 

 published, not more than one-half or a 

 third" — this is estimated much above the 

 truth — " of the lower surface is exposed 

 to the direct radiation from the fire, every- 

 thing being sacrificed to the close contact 

 of the fire with the water, and to the 



supposed efficacy of the air-carried heat 

 in the circuitous flues. In this respect 

 the conical boiler of Mr Rogers is a 

 decided improvement, as it exposes the 

 whole of its inner surface to the di- 

 rect action of the fire, while it retains 

 the error, as I deem it, of burning its 

 fuel within cold 

 walls." In the ac- 

 companying fig. 

 319, Mr Ainger 

 explains his idea 

 of efficient boiler- 

 setting : — " The 

 boiler in the figure 

 maybeconsidered 

 either as a hemi- 

 sphere or as a se- 

 mi-cylinder with 

 the ends closed, presenting to the fire in 

 either case an inverted chamber, from 

 which no gaseous matter escapes but by 

 descending to the lower edge, which, 

 being supported only at intervals, leaves 

 an almost uninterrupted channel for the 

 flame and smoke to play round the whole 

 upper surface. The fire is contained in 

 a brick case, so situated that every part 

 may radiate freely to every part of the 

 under surface of the boiler; and this 

 free radiation, to so large and so favour- 

 able a surface of heat, reduced by distance 

 to that degree of intensity which is 

 favourable to its absorption by the water, 

 will exhaust, I believe, a very large 

 portion of the effective power of the 

 fuel, which, under such circumstances, 

 may be of any description, and may 

 be burned subject to the most perfect 

 control. The dotted arrows show the 

 probable course of the flame and gaseous 

 products, the heating powers of which 

 must be sufficiently exhausted by the 

 whole upper surface of the boiler, and of 

 the arched vault in which it is contained : 

 their escape would of course be limited, 

 as usual, by a valve in the flue." 



" I feel confident," he continues, " how- 

 ever, that the heat obtained from the 

 smoke flues is very trifling compared with 

 that obtained from the radiation of the 

 fuel itself, provided that radiation has 

 fair play. Bad combustion not only pro- 

 duces less heat, but it interposes between 

 the fuel and the boiler a cloud sufficient 

 to intercept we know not how much of 

 the already impaired heating power ; and 



