PHYSICAL PROPERTIES OF ROAD-BUILDING ROCK. 
around. By means of a small one-fourth-inch steel chisel radial 
cuts are made in the saw one-eighth of an inch apart and one-eighth 
of an inch deep. The spaces between the cuts are then slightly 
opened by bending the projections alternately to the right and left. 
A mixture of vaseline and fine diamond fragments is inserted in each cut. 
All of the cuts are then closed with a pair of pincers and hammered 
down to the original thickness of the saw, thus driving the diamond 
dust into the metal. The diamonds are not ground to a powder, but 
are merely broken up into very fine fragments. A very small amount 
Fig. 5.— Details of Dorry hardness machine. 
of the mixture taken on the end of a toothpick is sufficient for each 
cut. Just enough vaseline is used to enable one to pick up the diamonds. 
The saw is mounted on a spindle (B, fig. 4) driven by the pulley 
(C) at 600 revolutions per minute from a motor (<9). The specimen 
to be cut is held in the V block (D), which is mounted on a swinging 
arm pivoted as at (E). The lower end of the saw runs continuously 
in water contained in the galvanized-iron pan (FF). 
Dorry hardness machine. 
The Dorry machine in use at the present time is a modification of 
the original French machine, and consists fundamentally of a circular 
steel disk (A, fig. 5), which is revolved in a horizontal plane by means 
17025°— Bull. 347—16 2 
