194 



" The dimensions of an ordinary furnace are 7 feet long 

 and 5 feet wide on the grate bars. If four times the fuel were 

 required to be consumed in the same time, (as is generally 

 used,) the grate bars must be four times the area, that is, 

 14 feet long, by 10 feet broad. I am of opinion a greater 

 evil would arise from the use of this furnace than what is 

 generally anticipated. Bicarburetted hydrogen, or what is 

 commonly termed 'fire damp,' reaches the explosive point 

 at a temperature of 500° or 550° Fahrenheit ; and having a 

 surface of fire equal to double the length to pass over, must 

 reach to a sufficient temperature for combination, and will 

 instantly take fire." 



