TRANSACTIONS OP THE SECTIONS. 107 



the necessary chair, was 100 lbs. The bevel in No. 2 rail might be given in the 

 wood-bearing : in No. 1 it was arranged in the casting of the chair ; this latter rail, 

 from having its top and bottom sides alike, had this advantage, that when it' began 

 to wear it might be turned round, or even turned upside down, which was a very 

 great advantage. He had for many years advocated wooden sleepers in preference to 

 stone, from his experience on the Dublin and Kingstown Railway, where he found that 

 the granite sleepers, the more massive they were the more injurious to the rails and 

 carriages. These had all been taken up, and longitudinal wooden sleepers laid down, 

 and the saving in expense of repairs would in a few years reimburse the outlay. The 

 railway only costs now 50l. per mile per annum for repairs, notwithstanding the 

 great traffic over it. The rails were the old 42 lb. rails, and, nevertheless, were still 

 used, in consequence of the advantage gained by the continuous bearings. He re- 

 commended keeping Evans's rail to the gauge by light iron rods passed through 

 holes in the rails, and secured by nuts : he thought these transverse ties should 

 never be used as supports. 



On Combustion of Coal, with a view to obtaining the greatest Effect, and pre- 

 venting the Generation of Smoke. By William Fairbairn. 



The author divided the subject into — 1st. The present state of knowledge as to 

 the combustion of fuel, particularly as regarded the boilers of steam-engines. 2nd. The 

 relation and proportion of the furnace and boiler. 3rd. The dimensions and height 

 of the chimney, and its proportion to the boiler and furnace. 4th. The working of 

 the furnace, and the mode of obtaining the nearest approach to maximum effect. 



In reference to the combustion of fuel, he observed, that our knowledge was 

 limited ; but, from the care of the fire being intrusted to persons of little knowledge 

 or experience, much lamentable waste occurred, from rapid combustion and the over- 

 working of boilers. Great loss also ensued from want of boiler space, and by work- 

 ing the engines to double what was intended by the maker, thus rendering it neces- 

 sary to force the fires to extract from the boilers sufficient steam. 2nd. With refer- 

 ence to the relation and proportion of the furnace and boiler. It was observed, that 

 in our present boiler furnaces, the ratio of fire-bar to flue surface is about 1 to 11, 

 or 100 square inches of grate-bar to 8 square feet of flue. But the Cornish engines 

 have much more flue surface, and other engines much less. He had always endea- 

 voured to give 12 - 5 feet of flue surface to 100 square inches of grate, or 1 to 18 nearly ; 

 and in marine boilers it is about 1 to 14"28. He found that, in a well-proportioned 

 boiler of 1 to 14, a pound of good coal evaporated 7'46lbs. of water, which was the 

 maximum effect produced in this district. By increasing the flue surface, the system 

 of slow combustion was established, and the evaporative power increased. 



Mr. Fairbairn then read a table of experimental observations respecting ten steam- 

 engines working in Manchester ; the mean results were, power of engine nominally 

 44"5 horses, working up to 57*3 horses ; area of grate, 48 - 2 square feet ; area of flue 

 surface, 542*5 square feet ; ratio of grate to flue surface, 1 to 1 1 ; height of chimney, 

 117 feet ; coal consumed in pounds per horse per hour, 10"5 (the table contained the 

 indicator diagrams of the several engines) . Thus it appeared that the ratio of fur- 

 naces to flues was of great importance. He had found that a marine boiler, with 100 

 square inches of grate bar, and 10 square feet of flue (exclusive of the bottom sur- 

 face of the flue), and having 40 feet of flue length from fire to funnel, generated an 

 ample supply of steam without forcing the fires. He also directed attention to a 

 table in which six different kinds of boilers were shown, with the ratio between their 

 heating or recipient surfaces and their cubic contents, from which it appeared, that 

 the best boiler in these conditions was the cylindrical boiler with internal tubular 

 flues. 2nd. The cylindrical boiler with internal flue. 3rd. Waggon boiler with in- 

 ternal flue. 4th. Waggon boiler without flue. 5th. Cylindrical boiler without flue ; 

 and last, the old haycock, or circular boiler. 



3rd division. There is no certain rule respecting the dimensions of chimneys. In 

 the Manchester district the custom was to place the chimney in some prominent po- 

 sition at a distance from the furnace, requiring underground flues of sometimes 400 

 feet long. This custom was injurious ; as, from damp, &c, the draft was diminished, 

 and it was necessary to have recourse to descending flues, which were contrary to 

 just principles. The chimneys should be placed near the boilers when practicable ; 



