Hot Blast in the Smelting of Lead. 169 



eels of ashes ; it is sufficient, if it exists in ignitible quantities, 

 and the particles are in ignitible proximity. It must be remem- 

 bered, that we should add to this fine combustible matter the 

 large coals and coarse powder separated by the sieve. 



It may be proper to add, that the wood we consume, is prin- 

 cipally beech, sugar tree, and hickory. 



Thus it appears : 



1. That wood ashes contain a considerable quantity of finely 

 divided coal. 



2. That the ashes may be sufficiently hot to ignite this coal, 

 without themselves being at red heat. 



3. That the progress of this ignition is slow ; and the combus- 

 tion may extend throughout a large mass of ashes, without warn- 

 ing, until it reach some inflammable material. 



I have assumed as true, for I suppose it will scarcely be denied, 

 that the loss in the contents of the crucible, was owing to the 

 consumption of carbon.* 



If my deductions from this humble, but I hope useful research, 

 are correct, it is not safe to deposit hot ashes even in the middle 

 of the largest bulk of cold ashes ; for although the fresh ashes 

 may not rest against wood, and may appear securely remote from 

 it, yet it is surrounded by and reposes upon combustible materi- 

 als, which may, as in these two instances, conduct the invisible 

 fire to inflammable bodies around, and box and buildings be in- 

 volved in sheets of flame. John. T. Plummer. 



June 12th, 1841. 



Art. XX. — On the use of Hot Blast in the Smelting of Lead. 



The reduction of lead ore is efl'ected in a great variety of fur- 

 naces, many of them primitive and simple ; others requiring great 

 expense in erection, and much practical experience in the man- 

 agement. Yet these latter often give no better results than the 

 original ' log furnaces' of our western pioneers. The great saving 

 of labor and certainty of product effected by the furnace described 

 below, induces the preparation of this article for publication. 



* Dr. Plummer does not state whether the ashes employed in his trial, were 

 heated to expel hygrometric moisture before weighing, which seems essential to 

 the accuracy of the results. — Eds. 



Vol.xLii, No. 1.— Oct.-Dec. 1841. 22 



