146 COMMERCIAL ROSE CULTURE 



two gases, oxygen and hydrogen, with carbon, which is a solid. 

 The two elementary bodies which give the heating power 

 to all fuels are carbon and hydrogen. It is said that one pound 

 of carbon will heat 14.220 Ibs of water 1 degree Fahr., while 

 one pound of hydrogen will heat 52.155 Ibs. of water 1 degree 

 Fahr. A unit of heat is an amount of heat required to raise one 

 pound of water one degree Fahr. 



Combustion is the term applied to the process of burning, 

 due to the oxygen of the air passing into a state of chemical 

 union with the carbon and hydrogen of the fuel. This combina- 

 tion always generates heat. One hundred and fifty-six cubic 

 feet of air must pass through the grate for every pound of coal 

 consumed ; about one-fifth part of this air is oxygen. 



Some grates are cast with insufficient air space. It is said 

 that one-third of the grate should consist of air space. Some 

 firemen wet their coal for the reason that heat resolves the 

 moisture into steam, and finally into carbonic oxide and hy- 

 drogen. If the draught supplied to the fire is sufficient, both 

 these gases will burn. 



One ton of average coal is equal to two cords of average 

 wood for steaming purposes. Coal is divided into two primary 

 divisions: anthracite, or hard coal, which does not flame when 

 kindled, and bituminous, or soft coal, which does. The reason 

 is the soft coal contains so much more hydrogen and ignites at 

 so low a temperature that it flames the instant it touches a hot 

 fire. Anthracite coal sometimes contains as high as 94 per cent, 

 of carbon. As this element decreases in amount it graduates 

 into a bituminous coal. The term anthracite is applied to coal 

 containing 80 per cent, or over of carbon. The maximum 

 consumption of coal for steam boilers is, with natural draught, 

 12 pounds per hour for each square foot of grate surface. 



The value of any fuel is measured by the number of heat 

 units which its combustion will generate. The two sources of 

 waste in fuel burned under steam boilers are, first, the gases 



