Processes in the Useful Arts. 161 



atmosphere. This is in the present case equal to about 15267 lbs. It 

 seems probable, that the momentum of the machine, and matter in motion, 

 overcomes a considerable portion of this ; but it will draw very largely on 

 our credulity, to imagine that no more steam is required to work the en- 

 gine than if this adjunct were dispensed with. An addition to the quan- 

 tity of steam necessary to the operation of the engine must certainly ob- 

 tain ; but as we have no precise information on the value of the inertia, we 

 have no data for calculating the increase of quantity required. We are also 

 much in the dark on the subject of the relative quantities of heat given 

 out by elastic fluids in a known period of time, when raised to various 

 degrees of temperature, and moving with different velocities. From such 

 an investigation, we may reasonably expect much valuable information, as 

 to the most economical application of heat, and the requisite motion of air, 

 in the flues of steam boilers, which might be derived. * 



2. On the quantity of heat disengaged by the combustion of a bushel of coal. 

 According to Dr Ure, one pound of coal will yield 5 cubic feet of gas ; 

 consequently a bushel (84 lbs.) will give 420 feet. Dr Henry considers 

 that 2 measures of carburetted hydrogen, 2 measures of carbonic oxide, 

 and 15 measures of hydrogen, constitute 19 measures of coal gas. Hence 

 the constituents of a bushel of coal are : Carburetted hydrogen— 

 45, 16 cubic feet, weighing 3,2206885 lbs. carbonic oxide. 



45, 16 3,2206885 lbs* hydrogen. 



329,68 1,7237 lbs- carbon. 



(75,9) say 75,5 lbs- 



Mr Dalton ascertained that the combustion of 1 lb- of hydrogen extricated 

 sufficient heat to melt 320 lbs* of ice. 



1 lb- rf carburetted hydrogen 85 



1 lb- — carbonic oxide 25 — ■ — 



1 lb' — charcoal - 40 



and it is well known, that the heat required to convert ice into water of 

 the same temperature, would have increased the temperature of an equal 

 quantity of water, about 150° ; consequently the heat extricated by the 

 combustion of the 



Hydrogen— 1,723? X 320 X 150 == 82737,6 



Carburetted hydrogen, 3,2206885 X 85 X 150 = 41063,178365 

 Carbonic oxide, 3,2206885 X 25 X 150 == 12077,581875 



I Carbonaceous matter, 75,5 X 40 X 150 = 453,000, 



58887 S°,36024 representing the number of degrees which the combustion 

 * The preceding investigation proceeds on the assumption, that the steam in the 

 cylinder is, when the steam valve closes, of the same density as that in the boiler ; 

 and in both the same as when the valve is opened ; but this is incorrect. There 

 is an increase of space, and the velocity of the piston increases. For the satisfaction 

 of those who wish to extend my calculations, the contents of the reservoir of steam 

 in the boilers, pipes, &c. is about 520 feet, the engine makes 7 stroke per minute, 

 and I imagine the working stroke to be made in about a 100 or 1 4-6 second of 

 time, the diameter of the steam valve being 8 inches. 



VOL. IX. NO. I. JULY 1828. L 



