CHARACTERISTICS OF PHILIPPINE COAL. 13 
of the grade of that from southeastern Batan Island, Dinagat, 
and Bulalacao in Mindoro, are unquestionably valuable fuel for 
local consumption. However, it is difficult to transport them and 
they can hardly be considered satisfactory steaming coals, al- 
though I believe they can be used without trouble if the furnaces, 
grates, and boilers are especially and properly designed and con- 
structed to insure more complete combustion of the coal and 
more perfect abstraction of the heat from the hot gases. In fact, 
any Philippine coal will give a greater efficiency if a style of 
furnace different from any now in use in the Philippines is em- 
ployed. The fire box of an ordinary furnace should be greatly 
lengthened, or some device planned for returning the unburned 
gases through the furnaces before passing up the chimney, in 
order most satisfactorily to use Philippine coal, or else a consid- 
erable portion of the fuel value of the volatile combustible 
matter, which usually approaches 50 per cent, will be lost. I 
have often urged ® the necessity of a setting with an elongated 
fire box and combustion chamber for burning this class of coal. 
The combustion space must be long and large enough for the com- 
bustible gases and air to mix thoroughly and to produce complete 
combustion. The United States Geological Survey has expressed 
the same opinion and further lays especial emphasis on the ne- 
cessity of an additional baffle wall.? Such a wall would undoubt- 
edly cause more perfect mixing and, therefore, more perfect 
combustion, which is the end desired. It is probable that eddies, 
such as it is desirable to attain in a reverberatory furnace, 
caused by any obstacle in the path of the gases, will greatly aid 
the mixing. Any scheme, which works in the direction of re- 
tarding the exit of the gases of the flame stream or of returning 
the unburned gases through the furnaces before passing up the 
chimney until combustion of the volatile, combustible matter is 
completed in the combustion chamber, contains the possibility of 
greatly increasing the efficiency of Philippine coals. Satisfact- — 
ory baffle walls would probably be of as much value as a consi- 
derable increase in the length of the fire box. A boiler with 
the same setting as those at the Bureau of Science, but arranged 
with different baffling forming a tile-roof furnace, has been used 
on Illinois coals and is said to run at capacities of from 50 to 100 
per cent without smoke. 
*Cox, A. J., This Journal (1906), 1, 877; Sec. A (1907), 2, 41. 
7 Bull. U. S. Geol. Surv. (1907), 325, 62. 
