688 KEW YORK STATE MUSEUM 



at Milwaukee, give more "uniform product and also use less fnei 

 (pi. 7). 



When the material is drawn from the bottom, it is commonly 

 sorted into normally burned rock, overburned or clinkered ma- 

 terial, and -underburned stone. At some works the clinker is 

 retained and treated separately; for, though it is of much greater 

 hardness than the normally burned stone, and requires more 

 powerful machinery to crush it, still it possesses a much higher 

 tensile strength. Three works in this state pulverize this clinker 

 and put it on the market under the name of Portland cement. 



There is usually a track running along the base of the kilns, 

 on which the cars are brought to receive the calcined stone. 

 These cars are then run up to the grinding rooms, where the 

 rock is reduced to powder. Several types of crushers and pul- 

 verizers are used, including Gates and Blake crushers,- Steadman 

 disintegrators, Sturtevant burstone and emery mills, Cammings 

 pulverizers, etc. 



The burned stone usually goes through a gradual process of 

 reduction, necessitating the use of machines for coarse, medium 

 and fine grinding, and the types used as well as their arrange- 

 ment is slightly different at each works, as mil be seen by refer- 

 ence to the description of the New York industry given in subse- 

 quent pages. In the natural cement trade there are several 

 standards of weight per barrel, as follows: Rosendale, 300 pounds 

 net; Pennsylvania, 280 pounds net in barrels, 200 pounds net in 

 sacks; Western standard, 268 pounds net."^ 



The Sturtevant roll jaw crusher (pi. 8) contains two steel 

 jaws with curved faces, pivoted at their lower end. The jaw^s 

 are operated by means of a toggle joint. It is claimed that this 

 crusher takes rocks of large size and reduces them at one opera- 

 tion to gravel and sand. A crusher with 6x16 jaws weighs 7 

 tons, and requires 10 horse power to run it. Its capacity is as- 

 serted to be 3 tons an hour of Portland clinker, when set to ^ 

 inch opening. 



iMin. ind. 6: 104. 



