When the percentage of volatile 
combustible to total combustible 
matter is equal to— Then a is equal to— 
25 102 
* 27.5 97 
30 92 
32.5 87 
35 82 
37.5 ‘i 
40 72 
42.5 67 
45 63 
47.5 59 
50 58 
§2.5 — 
55 56 
As yet we have not sufficient data thoroughly to test the accuracy of the 
formula when applied to coals of this region. Greater discrepancies 
between calculated and determined values have been noted on the coals 
analyzed in this Bureau than on the 150 others. In two of the deter- 
minations the results of the calorimeter tests fall 12 per cent below the 
calculated calorific values. These are both outcrop coals, and like many 
of our poor coals they probably contain carbonates which lose their carbon 
dioxide on ignition. In such cases the volatile combustible matter is 
largely volatile rather than combustible. The average variation of a 
series of eight, which is thought to be representative, is exactly 1 per cent; 
hence it is thought that the formula will give approximate results for 
average coals. 
The oldest and largest deposits of Philippine coal known are on Batan 
Island,’ Cebu, and Polillo, although it occurs in greater or less quantities 
in Negros, Zamboanga, Mindoro, Surigao, Rizal, Nueva Vizcaya, and 
Samar. 
In order to give a more accurate idea of these districts I have sum- 
marized the analyses made by this Bureau, and give them in the following 
tables. The calorific power has been figured according to the formula 
P= 81.5 C + aV where the values of a are as given above: 
*Smith W. D.: The Coal Deposits of Batan Island. Bull. Min. Bur., Manila 
(1905), 5. 
fad 
