28 BULLETIN 105, IT. S. DEPARTMENT OE AGRICULTURE. 
Experiment No. 6. — Penetration method — Hot, heavy oil. 
Location: From station 11+55 to station 12+62. 
Length: 107 feet. 
Method. — Owing to the difficulty in securing a surface of uniform 
texture with unscreened rock, it was decided to lay a section with 
new, screened material. The rock furnished from the pit was passed 
over a f-inch screen and the material retained was spread to a loose 
depth of 3 inches on the regraded road surface. Oil was applied at 
the rate of about 1 gallon per square yard, and this was sufficient to 
flush the voids. The penetration was evidently about 2 inches in 
depth over the entire surface of the section. From station 11+55 
to station 11+80 new rock screenings were used as a top dressing, 
and over the remainder of the section sand was used for this purpose. 
SUMMARY OF EXPERIMENTS AT MIAMI, FLA. 
An inspection of these experiments in December, 1913, showed Nos. 
1 and 2 to be in very bad -condition and demonstrated the impracti- 
cability of treating the original coralline rock roadway either by 
attempted penetration or strictly surface application of bitumen. 
Experiments Nos. 3 and 4 presented a very satisfactory appearance 
and there was little difference between them. No real failures were 
evident. Experiment No. 5 was not as satisfactory, although only 
two or three small holes had developed in it. Experiment No. 6, 
where new, unscreened rock was used, was in excellent condition and 
showed no indication of weakness anywhere on its surface. The 
cross section was true throughout and it had not worn perceptibly, 
although the untreated road immediately north of it had worn fully 
an inch during the preceding six months. 
The cost data are based upon the following unit prices for labor 
and materials : 
Foreman (per 10-hour clay) $3. 50 
Rollerman (per 10-hour day) 4. 00 
Pit boss (per 10-hour day) 3. 00 
Labor (per 10-hour day) 1. 50 
Teams (per 10-hour day) 6. 00 
Rock, in pit (per cubic yard) 15 
No charge was made for heating kettles, pouring pots, or other 
necessary equipment. 
Screened rock $1. 75- 
Sand, on work 1. 06 
Light asphaltic petroleum (per 
gallon) 162 
Heavy asphaltic petroleum (per 
gallon) 182 
