IX, A, 3 Dalburg and Pratt: Iron Ores of Bulacan 241 



conditioned almost wholly on the situation of the charcoal, since 

 the ore can be carried over a distance of from 2 to 3 kilometers to 

 better advantage than can the charcoal. 



SMELTING 



The smelter. — The smelter building or camarin consists of 

 a thatched gable roof about 16 meters wide by 22 meters long 

 set up so as to cover the furnaces and an additional space suf- 

 ficient for a train of molds, a storeroom for iron, a charcoal bin, 

 an ore pile, a core-burning pit, a blast apparatus, and rather 

 restricted quarters for the employees. At least three sides of 

 the building are left open, the fourth side usually being closed 

 by the charcoal bin which occupies about one-fourth of the 

 total floor space. 



Generally two furnaces, which are alternately in blast and in 

 repair, are set up in the center of the smelter. Behind, and 

 between them and the charcoal bin, is the one blowing apparatus 

 which serves each furnace in turn. A train of about 15 double 

 molds extends around the perimeter of the smelter. The store- 

 room for iron may be small, but is always strongly built and 

 is kept locked to prevent theft. The ore pile is about a meter 

 square, and serves as a breaking floor for reducing the ore to 

 the required fineness as well as a stock pile. A small pit at one 

 side of the furnaces is used to bake the clay cores which are 

 placed in the plowpoint molds, and near it the core maker works, 

 forming core, tuyeres, and molds, which are all of clay. 



The furnaces are cylindrical stacks 2.25 meters in height and 

 1.5 meters in exterior diameter. The upper part of the stack 

 to a depth of 1.75 meters is hollow, and constitutes the smelt- 

 ing crucible which is shaped like an inverted truncated cone 

 with a diameter of 1 meter at the top of the furnace and about 

 0.5 meter at the bottom or truncated section of the cone. The 

 stack is pierced from front to back through the bottom of the 

 crucible by a rectangular hole or runner, 12 centimeters deep 

 and 13 centimeters wide. The front end of this runner, con- 

 stricted somewhat by a temporary clay bridge, serves as a tap 

 hole for both iron and slag, while the rear end of the runner 

 admits a single tubular clay tuyere through which the blast 

 enters. Below and in front of the tap hole is a bench or step 

 upon which a hand ladle, also made of clay, is placed to receive 

 the iron upon tapping. 



The walls of the furnace are soft-burned brick made of clay 

 and set in a mortar of the same clay. The clay used for this 



