46 CEMENTS, LIMES, AND PLASTERS. 



Plant No. 6. (a) 1 nipper. 



(6) 1 cracker. 



(c) 4 runs of buhrstones. 



(d) 2 8-foot and 1 10-foot kettles. 

 Plant No. 7. (a) 1 Stedman disintegrator. 



(6) 3 runs of buhrstones. 



(c) 3 10-foot kettles. 



(d) 2 runs of buhrstones for regrinding. 

 Plant No. 8. (a) 1 Butterworth & Lowe nipper. 



(&) 1 cracker. 



(c) 4 runs of buhrstones. 



(d) 2 8-foot kettles. 



(e) 1 run of buhrstones for regrinding. 

 Plant No. 9. (a) 1 Blake crusher. 



(6) 1 cracker. 



(c) 5 runs of buhrstones. 



(d) 5 10-foot kettles. 

 Plant No. 10. (a) 1 Blake crusher. 



(6) 2 runs of buhrstones. 

 (c) 2 10-foot kettles. 



Rotary-cylinder processes. It will probably have been noted by 

 the reader that both of the plaster-calcining processes previously de- 

 scribed are discontinuous in operation and consequently expensive 

 in both time and fuel. These defects of the oven and kettle processes 

 are avoided in the rotary cylinder processes now coming into use in 

 both America and Europe. In the United States a rotary process 

 has been adopted in a number of New York plaster-plants, and has 

 been in practical operation for a sufficiently long time to demonstrate 

 its superiority over the kettle process. In Europe, to judge from a 

 recent description of the German plaster industry, rotary plaster cal- 

 iners have been used for a number of years and have proven entirely 

 satisfactory. 



Cummer system. Most of the American plants using the rotary cal- 

 cination process have been equipped on the system devised by the 

 F. D. Cummer & Son Co., of Cleveland, Ohio. 



The plan of a New York plant using this process is shown in Fig. 14. 

 This plant uses rock gypsum, and with the equipment shown produces 

 50 tons of calcined plaster per day of eleven hours, six men being re- 

 quired to operate the mill. The rock coming direct from the mine is 

 delivered into the jaw crusher A, where it is reduced so as to pass a 

 2^-inch ring. Elevator B carries the crushed rock from crusher to 

 screen C, which separates all material that will pass a 1-inch ring. The 

 tailings from the screen pass through the rolls D and meet with the 

 material which passes through the screen. All of the material now 



