STATE GEOLOGIST. 223 
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CHAPTER VI. 
MACHINERY AND TOOLS, 
It is not the object here to present anything upon the machinery 
used in the manufacture of cement, but upon the implements used in the 
- making of concrete, cement mortar, and mortar and concrete work. 
ROCK CRUSHERS, 
It is frequently cheaper to buy and install a rock crusher with the 
necessary power to operate it than it is to buy the stone already crushed 
and pay for shipping it from a distance and hauling it upon the work. 
Fig. 124.—Gates’ Gyratory Crusher, No. 7!/. 
There are a good many kinds of rock crushers in the market; a few 
| illustrating the different types will be presented here. Figure 124 shows 
