354 cox. 



and low efficiency. On the other hand, too little air results in low 

 efficiency due to incomplete combustion. 



Highly bituminous coals deposit much soot which may reduce the 

 efficiency of the heating surface, and the formation of scale is a factor 

 which needs close attention if maximum efficiency is to be attained. 

 With a change in efficiency other factors of the heat distribution also 

 vary. The radiation is especially variable with the size of the plant and 

 the temperature of the combustion chamber. 



The size of the fuel is a very important factor. The crumbling of coal 

 reduces its value for steaming purposes. There is a tendency of coal 

 from some parts of the Philippines to fall to pieces. Care must be 

 exercised in handling to prevent this. 



The moisture of the air is a large factor in the tropics. With an 

 evenly warm, almost saturated, atmosphere the amount of water entering 

 the furnace is enormous and considerably lowers the capacity and ef- 

 ficiency of the plant. 



The average of the calorific values of all the Philippine coals tested 

 is 6,003 '^ calories and that of the Australian coal "* purchased by the 

 Government and furnished to this Bureau for fuel is 6,614. In in- 

 dividual cases the calorific value of Philippine coal is as much as that 

 of the Australian coal and in one case showed an efficiency in this plant, 

 which is unfavorable to Philippine coal, within 3.75 per cent as great as 

 that attained when the Australian coal was fired. 



With respect to ash, clinker formation and the production of smoke 

 the Philippine coals are superior to any others ofEered on the Manila 

 market. 



^=9/5 calories=B. T. U. 



"This coal was tested in June, 1907 (tests Nos. 1 and 2, Table II). 



