GRIMSLEY. | Technology of Gypsum. 97 
Fig. 15. Gypsum Crusher, made at Enterprise, Kan. 
redressed. This operation requires skilled labor, and is a slow 
and expensive process. It is estimated to cost thirty dollars to 
dress the buhrs, and the operation takes about ten days. In 
order to avoid this difficulty other means of crushing have 
been employed. In some mills the steel flour mill rolls have 
been used, and it is claimed that these were successful. How- 
ever, they are not used in many of the rock mills. Another 
method of grinding has been invented by the Stedman’s Foundry 
and Machine Works, of Aurora, Ind., and is known as a lime 
disintegrator. This machine, as shown in Figures 16 and 17, 
consists of two cages with short cross-bars, and these cages 
travel at high speed in opposite directions. The gypsum is 
fed into the hopper to the center of the cages. The centrifugal 
force carries it between the bars of the cages. These bars passing 
each other in opposite directions beat the rock to powder by im- 
pact against the bars, and by the striking of the gypsum particles 
against each other. There is no danger of choking or clogging 
the machine, and the action is rapid. This means of grinding 
