IX, A, 3 Dalburg and Pratt: Iron Ores of^ Bulacan 203 



of January, but was resumed again on February 19 by Mr. 

 Dalburg and Mr. Pratt who remained in the field until the middle 

 of March. In the preparation of the manuscript for publication 

 it became apparent that additional geologic data which would 

 necessitate further field work were required. The stress of 

 routine activity in the division of mines delayed the accomplish- 

 ment of this additional work until December, 1913, before which 

 time Mr. Dalburg had severed his connection with the Bureau 

 of Science. Consequently, the supplementary field work which 

 required about one month's time devolved upon Mr. Pratt. Mr. 

 Pratt is also responsible for the preparation of the manuscript 

 which is based upon the notes of Mr. Dalburg, Mr. Nable, and 

 himself. 



This investigation was undertaken with the idea of aiding the 

 established Filipino iron-smelting industry and of determining 

 the possibilities of commercial exploitation on a larger scale. 

 The plan included (1) a study of the geology of the ore deposits 

 in its bearing upon a determination of the quantity and quality 

 of the ore available; (2) a study of the factors which would 

 affect the mining and smelting of the ore, such as transporta- 

 tion, fuels, fluxes, power, market, etc.; and (3) a study of the 

 native smelting process with a view to its possible improvement 

 and expansion. The smelting process, however, was found to 

 afford so large a field for investigation that it will be taken up 

 in a separate paper to be published later. 



The detailed work involved was rendered very difficult by 

 reason of the situation of the ore deposits in a heavily wooded, 

 mountainous, and almost impassable region, together with the 

 lack of an accurate map and the entire absence of subsurface 

 mining operations. The funds available did not permit the 

 making of a complete accurate map of the district, and it was 

 therefore necessary to rely upon the existing maps supplemented 

 by compass traverses.^ 



In the absence of underground development the estimates of 

 the tonnage in the ore reserves are of necessity based upon 

 the observed areas of the outcrops and geologic nature of the 

 deposits. A magnetic survey was attempted in the vicinity of 



' The map accompanying this report was compiled from original compass 

 surveys made in connection with this study, surveys by the Spanish Inspec- 

 cion de Minas, by the Engineer Corps of the United States Army, and by 

 McCaskey. McCaskey's map is very good over parts of the area, but a 

 glaring defect is the inexplicable distortion by which the Camaching District 

 is located north of the town of Sibul; its true position is far to the south 

 of this town. 



