28 College of Forestry 



special doors and the vapors are drawn off by exhausters 

 through wooden ducts. This practice was followed especially 

 in Pennsylvania and in Wisconsin, where an abundant supply 

 of the desirable hardwoods was found in a location near blast 

 furnaces where pig iron was produced. Pig iron, manu- 

 factured by the use of charcoal is considered far superior to 

 that made by coke. The pig iron made with charcoal com- 

 monly bring about $5 a ton more than that manufactured 

 with coke. The brick kilns were usually built to hold 50 to 

 90 cords each and were charged and discharged by hand. 

 The complete manufacture of charcoal by the brick kilns 

 including charging and discharging required from 15 to 25 

 days. The heating necessary to distill the wood is supplied 

 by the combustion of part of the charge within the apparatus, 

 in the same way that charcoal is made in the open air pit. 

 The yield of charcoal by this method is somewhat below tliat 

 manufactured in the retorts or ovens and is generally con- 

 sidered inferior in grade. The brick kiln is only desirable 

 when the chief product is charcoal and transportation facili- 

 ties are not available or the market is too distant for the 

 other products of wood distillation, such as wood alcohol and 

 acetate of lime. Where other forms of fuel, such as natural 

 gas and coal are out of the question and the manufacture of 

 charcoal is desired, it is also commonly used. 



Most of the brick kilns in operation are in Michigan and 

 Wisconsin, where charcoal is in great demand in connection 

 with iron furnaces. There are no brick kilns operating in 

 !N'ew York at th^ present time for the manufacture of 

 charcoal. 



Iron Retorts. 



The iron retort followed the brick kiln and was the first 

 device invented whereby the vapors from the carbonization 

 of wood are collected on an efficient basis and distilled in the 

 form of pyroligenous acid and later refined into wood alcohol, 



