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. 



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Wt ' 



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 



