396 



JMiscellanies. 



an iron cap — -which cap must be removed at each successive empty- 

 ing and filling of the pit — some tubes leading from the top of the 

 ground to the bottom of the pit served as vents. From the nature 

 of this construction, it is evident that the size must necessarily be lim- 

 ited to a very few cords of wood — say five or six at most. — This 

 size might answer very well for the extraction of pyroligneous acid, 

 to which purpose M. de la Chabeaussiere applied his kiln — or for a 

 blacksmith who consumes but a small quantity of coals ; but would 

 be no more than a plaything in works where the daily consumption 

 is from one thousand to fifteen hundred bushels or more. 



It occurred to me that, by 

 building kilns above ground, 

 so that all the vents could be 

 come at with facility, and 

 arching the top over in the 

 form of a dome, leaving one 

 or more openings in the side 

 for the admission of wood 

 and the extraction of coals, 

 (which are closed during the 

 operation of charring,) they 

 might be constructed of al 

 most any size that might be 

 desirable. The result of the 

 experiment justified my most 

 sanguine expectations. A 

 kiln of thirty feet diameter, 

 and nine feet high to the 

 spring of the arch, and which 

 holds fifty cords of wood, has 

 been several times filled and 

 charred, and has uniformly 

 yielded from fifty five to sixty 

 bushels of coals to the cord,* 

 of a quality, far, very far su- 

 perior to coals made in the ordinary way. From the manner of 

 making these coals, they must be entirely Iree from stones and dirt, 



* Colliers, in the woods, usually compute the yield oF coals attlie rate of one hun- 

 dred bushels to two and a half cords of wood, or forty bushels to the cord — but I be- 

 lieve that, as a general average, one hundred bushels to three cords of wood, would 

 be nearer the truth. 



