580 TRANSACTIONS OF THE 



or in fact fuel underneath, the previous heat having decomposed 

 water into gases, which exploded on the introduction of a candle. 



I think a valve might be arranged in such a manner as to admit 

 air in sufficient quantity to choke the condenser of the engine, 

 shut off the water and throttle valves and open the blow valves. 

 If this were accomplished, the fly wheel would make but one 

 revolution instead of five as is now the case. 



The effect of a boiler is not much influenced by its form. The 

 size always governs the quantity of steam it is to make, that is 

 the surface brought to bear the influence of the fire. The cylin- 

 drical boiler, by the use of two pounds of coal will produce seven 

 pounds of steam. No other form of boiler probably will make 

 more steam from that quantity of coal. The great advantage that 

 the tubular boiler has over all others is that it requires less 

 space. To produce steam for a two horse power, twenty-four 

 square feet of boiler surface should be exposed to the gases or 

 heat issuing from the furnace. A very high heat in the gases 

 must be disadvantageous if we desire to economise fuel, at all 

 events it should be expended pbout midway of the boiler, so that 

 when it passes into the flue its temperature ma}^ be about equal 

 to the metal of the boiler, as the heat conducted away in the gas 

 is' the principal loss. This matter should be well considered 

 when the boilers are set, and likewise the form and length of the 

 flues. The size of the grate is of immense importance, as it is 

 well known that combustion can be perfect only under peculiar 

 conditions. As fuel can only be used to great advantage when 

 burned under a very high temperature, sufficient in fact to gene- 

 rate carbonic acid gas, which requires intense heat, if combus- 

 tion is imperfect, as it must be at a low heat, a very large part of 

 the fuel is necessarily changed into carbonic oxide, which cer- 

 tainly does not afford as much liberated heat as carbonic acid by 

 one-half. The furnace must, therefore, be so arranged under the 

 boiler as to produce combustion under intense heat. Non-con- 

 duetors should be used as lining for the fire boxes, such as brick, 

 *and these should be light colored, as black substances above the 

 fire prevent the formation of carbonic acid. Fuel should be so 

 used that twice as much air as is required for combustion should 

 pass through the fire. To accomplish this there nuist be enough 

 heat to convert all the fuel burnt into carbonic acid gas. If car- 

 bonic oxide is form?d, more coal is consumed and less heat given 

 out. 



The condition requisite for ebullition is that bubbles of air 

 shall present on their outward surfaces the coherent requisite for 



