100. Why, when the coals have become heated, will the hydrogen burst into flame?
Because the carbon of the coals, and the oxygen of the air, have begun to combine, and have greatly increased the heat, and have produced a rapid combustion, so nearly allied to flame, that it ignites the hydrogen.
101. What temperature is required to produce flame?
That depends upon the nature of the combustible you desire to burn. Finely divided phosphorous and phosphorated hydrogen will take fire at a temperature of 60 deg. or 70 deg.; solid phosphorous at 140 deg.; sulphur at 500 deg.; hydrogen and carbonic oxide at 1,000 deg. (red heat); coal gas, ether, turpentine, alcohol, tallow, and wood, at about 2,000 deg. (incipient white heat). When once inflamed they will continue to burn, and will maintain a very high temperature.
Smoke consists of small particles of carbon of hydrogen gas, and other volatile matters, which are driven off by heat and carried up the chimney.
103. Is it not a waste of fuel to allow this matter to escape?
It is, as it might all be burnt up by better management.
104. How may the waste be avoided?
By putting on only a little coals at a time, so that the heat of the fire shall be sufficient to consume these volatile matters as they escape.