108 REPORT — 1842. 



and descending, and even horizontal flues, avoided as much as possible. With respect 

 to the height of chimneys, we can hardly err in going too high, as the draft is as the 

 height of the column of rarefied air ; we thus can always obtain a plentiful supply 

 of air to our fires. Some persons consider that the chimney should be widest at the 

 top, to allow of the free passage of the rarefied air ; but this was inconvenient in 

 building, and he had not found it to give any advantage. In general, chimneys, in 

 consequence of their great height, were built broad at the base and tapered towards 

 the top, both externally and internally. This was also disadvantageous, as it throt- 

 tled the draft. He found parallel flues, well-plastered, to be the best in every respect. 

 4th. With respect to the best methods of working the furnace, and obtaining the 

 nearest approach to maximum effect, he had endeavoured to obtain, by direct experi- 

 ment, the comparative consumption of coal, in Mr. Williams's plan, and the common 

 practice. For this purpose he got Messrs. Hetherington and Co. to attach Mr. Wil- 

 liams's apparatus to their boiler in January last. This boiler supplied a 12-horse en- 

 gine, and gave motion to machinery, tools, &c. During the experiment great care was 

 taken, to keep the work steady, and to regulate the firing, so as to give equal chances 

 to each system. The result was slightly favourable to the old plan ; but as there was 

 reason to' doubt its accuracy, the trial was repeated, when the results showed a saving 

 of T y,/ in favour of the new system ; or, by taking the average of all the experiments, 

 the consumption on the new system was to that on the old as 292 to 300, or about 

 4 per cent, in favour of Mr. Williams's plan on the score of expenditure ; while, on 

 the point of its abating the nuisance of smoke, no doubt could arise. 



On testing the Efficacy of the several Plans for abating the Nuisances from 

 Smoke by effecting a more perfect Combustion. By C. W. Williams. 

 The usual mode of measuring combustion, he stated, was the ascertaining the 

 quantity of water evaporated by each pound of fuel ; yet this was the most fal- 

 lacious of all tests, as from the varieties of boilers and the differences in their eva- 

 porative powers, their results were so at variance as not to be depended on. As re- 

 gards the nuisance, the appearance of the chimney was a sufficient test : but when 

 the question of economy was considered, a very different class of tests was required. 

 Economy has reference to two distinct objects; namely, 1st, the obtaining the 

 largest quantity of steam from a pound of coal ; and 2nd, obtaining such quantity 

 of steam in the shortest time. Thus economy has reference to fuel and to time ; and 

 it is important to observe, that the economy in the one is inversely as that of the 

 other. Mr. Williams observed that economy in fuel, that is, obtaining the highest 

 evaporative effect from each pound of coal, may be the ruin of the manufacturer ; 

 for if his engine requires a given weight of water to be converted into steam within 

 a given time, if such quantity be not supplied the engine cannot do the required 

 work. Mr. Williams referred to a variety of experiments made by himself, Mr. 

 Parkes, Mr. Wickstead and others, showing that, by quick or slow combustion of 

 coal, the quantity of water evaporated from the same boiler, and by the same fur- 

 nace', varied considerably. This view of the question showed the necessity for 

 distinguishing between the boiler and the furnaces ; for though heat may be gene- 

 rated by a more perfect combustion in the furnace, yet, if the boiler is not equal 

 to its absorption, the remainder will pass by the chimney and be lost ; and Mr. Wil- 

 liams showed that exactly in the degree in which the heat was increased in the flues, 

 was the waste heat also increased by the chimney. If then we look to the quantity 

 of steam generated, we must refer to the boiler and its evaporative faculty ; but if 

 we look to the quantity of heat generated, we must refer to the furnace and flues. 

 Mr. Williams then urged the importance, in testing any plan of combustion, of look- 

 ing as well to the temperature of the escaping products by the chimney as to the 

 quantity of steam generated in the boiler. The true test then is to be found in 

 ascertaining the quantity of heat generated rather than of the steam produced ; and 

 without any reference whatever to the boiler. Mr. Williams referred to an ingenious 

 and practical mode adopted by Mr. Houldsworth for estimating the temperature in 

 the flues of a boiler. 



Mr. J. Juckes exhibited and explained the model of his furnace for consuming 

 smoke and economizing fuel. His grate bars form an endless chain passing over 



