different kinds of Coal-gas Burners^ <5rc. 235 



Using in all 2 gallons of water, by 2 feet of gas, the tempera- 

 ture of the fluid when mixed was 122. The air, as it escaped 

 from the tube, was of the same temperature as that of the 

 room, shewing that the whole of the heat generated by the 

 combustion was taken in by the water, with the exception of 

 that lost by radiation downwards from the burner, which is 

 not great. 



With respect to the heat thus lost, it must depend on the 

 mode of combustion. When the flame is small, it may be put 

 far up in the cavity of the boiler ; but when it is large, it must 

 be placed lower down, to admit of sufficient current, otherwise 

 there is smoke. The farther up in the cavity the better, pro- 

 vided there is no smoke ; but when a small flame is used, 

 owing to the time required, there is a loss of heat from the 

 boiler, so that the one, to a certain extent, counter-balances 

 the other. By having recourse to these contiivances, it is 

 evident that much of the heat that would otherwise escape 

 may be successfully applied ; at the same time, for common 

 purposes, these methods are not likely to be adopted, because 

 they make the apparatus complicated, and their use is attend- 

 ed with trouble. A boiler of the form I have already describ- 

 ed, may, however, be easily employed, and will answer most 

 of the purposes for which gas, as a source of heat, is likely to 

 be used. With this apparatus, I have found, taking the ave- 

 rage of numerous trials, that, by the combustion of 1 foot of 

 gas, 1 gallon of water may be raised from 50 to 105, or even be- 

 yond that, consequently 3 feet would bring it up to the boiling 

 point. To boil off^ the whole of the water would require 5J 

 times as much as is necessary to raise it from 32 to 212 

 and 3 X 5.5 = 16.5, which added to 3 = 19.5, but less than 

 this would be required, were the water at 50 instead of 32. 

 In one trial I found that 1 gallon might be boiled off" by 16.5 

 feet, and I consider this as the utmost that can be expected, 

 allowing for the loss always consequent on the use of gas by 

 any of the methods mentioned. Of course, in stating this as 

 the quantity to be evaporated, it applies solely to the gas with 

 which I operated. 



From these data we are enabled to ascertain whether gas 

 is, or is not, an economical source of heat. Let us i^uppose that, 



