Tests Made. 
251 
way the surface was broken to pieces five or six times and the 
average number of blows required to break up the different 
mixtures was taken as representing their relative surface 
strength, the highest being scaled as one hundred. Then the 
same process was repeated with the difference that this time 
the whole depth of the mass, about two and one-half inches, was 
broken up into its original condition of loose gravel and fine 
material, and the results scaled in the same way as before. The 
average of these two ways of testing may be taken as indicat¬ 
ing approximately the value of the different materials and com¬ 
binations for use as cementing material on roads. The accom¬ 
panying table shows the results obtained. 
Coarse 
material. 
Cement. 
Strength 
of surface. 
Strength 
of whole 
mass. 
Value. 
1 
Gravel. 
Diabase 34? blue lime¬ 
stone 34 . 
100. 
100. 
100. 
2 
Gravel. 
Diabase^, sand % . 
81.6 
75.5 
78.6 
3 
Gravel. 
Fine granite 34? blue lime¬ 
stone 34. 
38.3 
86.5 
62.4 
4 
Gravel. 
Fine granite 34? sand 34 • 
48.9 
75.6 
62.3 
5 
Gravel. 
Diabase. 
52.0 
72.2 
62.1 
6 
Limestone. 
Blue limestone. 
58.8 
58.8 
58.8 
7 
Gravel. 
Fine granite. 
51.6 
60.1 
55.9 
8 
Gravel. 
Medium granite 34? blue 
limestone 34..... 
53.3 
55.6 
54.5 
9 
Gravel. 
Coarse granite 34? blue 
limestone 34. 
45.3 
62.2 
53.9 
10 
Gravel. 
Gravel. 
43.4 
44.0 
43.7 
11 
Limestone. 
Buff limestone. 
48.6 
38.6 
43.6 
12 
Gravel. 
Medium granite. 
42.4 
44.8 
43.6 
13 
Gravel. 
Sand... 
45.0 
27.8 
36.4 
14 
Gravel. 
Coarse granite. 
25.9 
28.7 
27.3 
With the exception of the two kinds of limestone all the stones 
used in the experiments were selected from the glacial drift. 
The diabase was a compact dark green or nearly black rock. 
The granite of No. 3 was a fine-grained dark variety containing 
a large proportion of hornblend, no mica and but little quartz. 
Most of the crystals were not a sixteenth of an inch in di¬ 
ameter. The granite of number 8 was a little coarser, with 
crystals ranging up to an eighth of an inch in diameter. 
It contained rather more quartz and less hornblend than 
