122 Chemistry. [Lecture 28. 



able improvements have lately been made in this 

 instrument. 1 



The reverberator^ furnace for melting iron, See. 

 has a square fire-place, and an oblong oven, from 

 the further extremity of which rises a long vent; 

 and the furnace beating down the flame on the 

 metal causes a violent heat. In fig. 18. A is the 

 fire-place, B the dome and chimney, which is 

 moveable, and which incloses C, the vessel con- 

 taining the metal, which by this contrivance is 

 surrounded by the flame. 



The pottos kiln has a large cavity of a conical 

 form ; the flame rises in the bottom of the cavity, 

 and flies out at the top like a torrent of liquid 

 fire. This will do when a moderate heat is re- 

 quired; for stone ware or porcelain the kiln 

 must be provided with six or eight furnaces for 

 sending up flame. 



The glass-house furnace must be constructed 

 in such a manner as to allow the workmen to 

 have free access to it without diminishing the 

 heat. 



The reason why brick furnaces often crack is, 

 their internal parts being more heated and con- 

 sequently more expanded than the external : to 

 prevent this the furnace should be heated and 

 cooled gradually, at least till properly seasoned. 



The furnaces employed in heating retorts only 

 differ in a contrivance for heating the vessel 

 slowly and equally over the surface. These pro- 



