118 REPORT 1844. 



In some cases it may however be necessary to overtake and effect the ig- 

 nition of such gases as may escape over the bridge unconsuraed, and for this 

 purpose, in some descriptions of hght coal, it may be desirable to admit 

 about half the quantity of air used in the combustion of the bituminous kinds. 



The ultimate results are, therefore, — 



A perfect knowledge of the properties of the fuel used, and judicious 

 management in working the fires. 



An increase in the area of recipient surface of the boiler in the ratio of 

 the furnace as 1 to 18, or what is the same thing, a reduction of the grate- 

 bar surface to that proportion. 



A constant supply of air (through a fixed aperture) of 1^ square inch to 

 every foot of grate-bar in common boilers, when burning bituminous coal j 

 and half that area when using splint coal. These openings should however 

 be regulated in the first instance by hand, until the mean or maximum effect 

 in reference to the fuel is obtained. 



A complete covering of felt, or some other non-conducting substance, to 

 be applied to the exterior parts of the boiler, and the flues to be well-pro- 

 tected on all sides from the external air. 



On a strict observance of these rules will depend the question of smoke or 

 no smoke, and also whether an important oeconomy in the use of fuel shall 

 or shall not be effected. We are assured, from the experimental facts already 

 recorded, that both these objects can be accomplished, and it rests with the 

 community to determine how far they shall be carried into effect. 



At the time of entering upon this investigation, it was my intention to 

 have confined it within exceedingly narrow limits : it was however found to in- 

 crease in interest as I advanced ; and from the nature of the subject, and 

 the number of considerations connected therewith, I became involved in a 

 long and important inquiry ; an inquiry progressively developing new fea- 

 tures, and admitting of no curtailment except only in such matters as did 

 not directly bear upon the subject. As it is, I fear I have but imperfectly 

 discharged the duty entrusted to my care : it is however done honestly ; 

 and trusting to future developments in the hands of superior writers, I close 

 the report under the impression that the preceding investigations may direct 

 public attention to the extension of our knowledge and improvement of our 

 practice in the combustion of fuel and the prevention of smoke. 



Manchester, Nov. 30, 1844. 



Note by Mr. Fairbairn, beirig an Appendix to the preceding Report. 



During the progress or about the close of the above report, I found that 

 my friend and former pupil Mr. A. Murray had communicated a paper on 

 a similar subject to the Institution of Civil Engineers, entitled " The Con- 

 struction and proper Proportion of Boilers for the Generation of Steam." 



Mr. Murray has had many opportunities of judging of the best forms and 

 proportions of marine boilers, and, from the facilities afforded in his profes- 

 sional avocations at the Royal Dockyard, Woolwich, I am induced to quote 

 a iew of his observations relative to the area of the flue, bridge, chimney, 

 &c., which have in some degree been omitted in the preceding report. In 

 treating of the quantity of air entering into combination with the volatile 

 products of pit coal, Mr. Murray states, that " The quantity of air chemi- 

 cally required for the combustion of 1 lb. of coal has been shown to be 

 150*35 cubic feet, of which 44'64' enter into combination with the gases, 

 and 105'7l with the solid portion of the coal. From the chemical changes 



