MANUFACTURE OF NATURAL CEMENTS, 



237 



or another. Within the past few years modern grinding machinery 

 has been introduced at a few plants and has given such satisfactory 

 results that no natural-cement manufacturer can afford to disregard 

 the innovations. 



The gain in strength due to increased fineness of grinding is well 

 shown by the following data, for which I am indebted to the Western 

 Cement Company, of Louisville, Ky. A year or two ago this com- 

 pany replaced millstones in one of its best plants by tube mills, and 

 increased the fineness from about 76 per cent through a 100-mesh sieve 

 to about 90 per cent through 100-mesh. With mortar briquettes, 

 1 cement and 2 sand, this gave the following results: 



Actual mill equipments. The variations in practice which now 

 exist can best be understood by reference to the following data on the 

 actual equipments of a number of the best American mills: 



Gates crusher -> 



Lindhard kominuters 1 1500 bbls. per day. 



2 Davidsen tube mills J 



5 McEntee crackers } ., , 



> 1600 bbls. per day. 

 16-run Esopus millstones J 



1 coarse pot crusher > 200 bbls. per day 



fine pot crusher I (run only about 



Williams mill J one third time). 



1 Williams mill. . . . . } . , 



16-foot Bonnot tube mill.. . . ) 10 bbls - P er ^ 



Sturtevant crushers. 



Cummings grinders. 



10-run millstones, iron plates. 



10-run Esopus millstones. 



Pot crushers. 



Esopus millstones. 



Gates crusher -i 



dry-pans [ 800 bbls. per day. 



Davidsen tube mill J 



1 pot crusher } _, 



> 500 bbls. per day. 

 1 Williams mill J 



Stedman disintegrators. 

 Griffin mills. 



