40 CEMENTS, LIMES, AND PLASTERS. 



Within the past few years sectional kettle-bottoms have been in- 

 troduced quite extensively. A kettle of this type is shown in Fig. 11, 

 in which the kettle-bottom is composed of a central circular section 

 and six other sections fitting around it. These sections are made of 

 cast iron. The principal merit of this design is that in case any section 

 of the kettle-bottom burns out, it can be replaced without disturbing 

 the kettle or brickwork. 



FIG. 11. Kettle with sectional bottom. (Des Moines Mfg. Co.) 



The kettle, which is placed on the kettle-bottom, is of boiler iron 

 f to f inch thick, and is commonly 8 to 10 feet in diameter and 6 to 

 8 feet deep. Such a kettle holds about 7 to 12 tons of raw material, 

 producing from 5^ to 10 tons of plaster. The kettle has two or four 

 flues 12 inches in diameter, placed horizontally about 8 inches above 

 the crown of the kettle-bottom and separated externally about 6 inches. 

 After the kettle has been set, brick masonry is erected around it, gradu- 

 ally converging at the top to meet the top rim of the kettle. The 

 first floor of the mill is usually built around the kettle about a foot 



