CEMENTATION 



adjusted by thumbscrews to give a 

 a fraction of a millimeter to 10 cm. 



9 



varying from 

 ow cone at its 



ELEVATION Of HAMMER LIFT AND DEVICE FOF} TAPPING HAMMER 



FIG. 4. Impact machine to determine cementing value of rock. 



lower end, into which the cone of the hammer head is thrust when the 

 hammer is lifted by the crosshead (/). When the cone of the ham- 



