STATE GEOLOGIST, : 287 
This tends to show that it 1s possible to grind sand or sandstone 
sufficiently fine for cement purposes, if either more time is allowed for 
the grinding or it is carried on separately. It will be noticed that the 
curve of “chemically available’ material does not change materially in 
its slope, which seems to indicate that in 5-4 the time, that is, in about 310 
minutes, practically all of the quartz would have been rendered chemically 
available. The most important fact brought out by this experiment is 
this uniform slope, for if the output of really fine material were to decrease 
as the grinding, that is, the bulk of fine particles increases, the feasibility 
of the fine grinding would seem more or less problematical. It was 
intended to carry out the experiment with coarse quartz sand, clay and ~ 
limestone mixtures, but the breaking of the mill due to unusually severe 
work put a stop to the experiments. 
