PHYSICAL PROPERTIES OF ROAD-BUILDING ROCK. 
that the axes of the cylinders are 
inclined at an angle of 30° with 
the axis of rotation. These cyl- 
inders are 20 cm. in diameter and 
34 cm. in depth inside. The shaft 
is set in the three bearings DDD 
and carries at one end a revolution 
counter which is not shown in 
the cut. 
Balance weighing to 5 kilograms 
and sensitive to 0.5 gram. 
This balance should preferably be 
equipped with a supplementary 
scale pan, measuring 10 inches in 
diameter and 2 inches high, and a 
suitable counterweight. This will 
make it possible to weigh the en- 
tire sample in one operation. 
50-pound anvil. 
Stone hammers. 
Several 3-quart enameled iron 
pans. 
Sieve. 
The sieve should preferably be 
brass rimmed and reinforced in 
order to withstand heavy usage, 
about 16 inches in diameter, with 
square mesh of one -sixteenth 
(0.0625) inch clear opening. 
Drying oven. 
METHOD. 
The material is broken into pieces 
as nearly of the same size and 
shape as practicable, so that ap- 
proximately 50 pieces shall weigh, 
after thorough drying, to within 1 
gram of 5,000 grams. In no case 
should the number of pieces exceed 
60 or be less than 40. Care should 
be taken to use only freshly 
broken fragments, as pieces with 
rounded edges greatly affect the 
results. Although the size of 
the individual pieces composing 
a sample varies theoretically 
