3 BULLKTIX 1210, V. S. DEPARTMENT OF AGRICULTURE. 
dimensions.' Tlie ends of the cylinders may be sawed by means 
of a hand or diamond saw.' or in any other way which will not 
induce incipient fracture, but shall not he chipped or broken off 
With a hammer. After sawing, the ends of the specimens shall 
be ground plane with water and carborundum or emery on a 
cast-iron lap until the cylinders are 25 millimeters in length. 
Impact 5. Any form of impact machine which will comply with the 
machine. following essentials may be used in making the test : 
(a) A cast-iron anvil weighing not less than 50 kilograms, 
firjnly fixed upon a solid foundation; 
<M A hammer weighing 2 kilograms, arranged so as to fall 
freely between suitable guides; 
{(■) A plunger made of hardened steel and weighing 1 kilo- 
gram, arranged to slide freely in a vertical direction in a sleeve, 
the lower end of the plunger being spherical in shape with a 
radius of 1 centimeter : 
(d) Means for raising the hammer and for dropping it upon the 
plunger from any specified height from 1 to not less than 75 centi- 
meters, and means for determining the height of fall to approxi- 
mately 1 millimeter ; 
(e) Means lor holding the cylindrical test specimen securely on 
the anvil without rigid Lateral support, and under the plunger in 
such a way that the center of its upper surface shall he tangent to 
the spherical end of the plunger at its lowest point throughout the 
test. 
6. The test shall consist of a 1 -centimeter fall of the hammer for 
the first blow, a 2-centimeter fall for the second blow, and falls 
increasing by 1 centimeter for each succeeding blow until failure 
of the test specimen occurs. 
7. The height of fall in centimeters at failure shall be taken as 
the toughness of the test specimen. The individual and the aver- 
age toughness of three test specimens shall he reported when no 
plane of structural weakness is apparent. When a plane of struc- 
tural weakness is apparent, the individual and average toughness 
of the three specimens in each set shall he reported and identified. 
Any peculiar condition of a test specimen which might affect the 
result, such as the presence of seams, fissures, etc., shall he noted 
and recorded with the test result. 
TEST FOR SOUNDNESS OF COARSE AGGREGATE. 
Immerse 10 small pieces (total weight about 1,000 grams) of the 
rock in a saturated solution at 70° F. of sodium sulphate 
(Na 2 S04) for 20 hours, after which place them for 4 hours in a 
drying oven maintained at 100° C. Repeat the treatment five 
times. Note the condition of the rock as to soundness at the end 
of the test. 
Samples which exhibit marked checking, cracking or disintegra- 
tion shall he considered to have failed in this lest. 
LITHOLOGICAL COUNT OF GRAVEL PARTICLES. 
From 100 to 200 pieces of gravel stones, selected at random. 
ranging in size from one-half to 2 inches shall he separated into 
the various rock types a in! the percentage composition noted. 
Notr.— This is a simple tost which, especially in dealing with the 
northern glacial gravels, will obviate considerable laboratory work. 
There i^ no Single laboratory test for this type of material which 
will give such conclusive results as to quality of the material as this 
when the adjacent bedrock and direction of the glaciatiou are known. 
The form of diamond drill described in Bulletin No. 347. T. S. De- 
partment of Agriculture, pp. 6—7, is recommended, and should prove 
satisfactory ii the Instructions are strictly followed. 
'A satisfactory form of diamond saw is described in Bulletin No. 347, 
U. S. Department of Agriculture, pp. 7-9. 
