Coals, at the highest furnace temperature, radiate much heat, whereas gases ignited at and beyond the bridge wall radiate comparatively little heat—it is a law in nature for a solid body highly heated to radiate heat to another solid body.
Dry and Clean is the condition in which the boiler should be kept, i.e., dry outside and clean both inside and out.
To haul his furnace fire and open the safety valve before seeking his own safety or the preservation of property, is the duty of the fireman in the event of fire threatening to burn a whole establishment.
Many, now prominent, engineers have made their first reputation by remembering to do this at a critical time.
When Water is Pumped into the boiler or allowed to run in, some opening must be given for the escape of the contained air; usually the most convenient way is to open the upper gauge cock after the fire has been lighted until cloudy steam begins to escape.
In a summary of experiments made in England, it is stated that:—
“A moderately thick and hot fire with rapid draft uniformly gave the best results.
“Combustion of black smoke by additional air was a loss.
“In all experiments the highest result was always obtained when all the air was introduced through the fire bars.