DUST PREVENTION AND ROAD PRESERVATION, 1916. 45 
In September, 1916, a treatment of crude oil was applied to the 
surface by the county road authorities. At the time of the inspection 
the surface was in good condition, except for one spot 115 feet from 
the north end of the sections. This spot is about 4 feet wide and 3 
feet long and shows excess bituminous material and sand varying 
in thickness from three-quarters inch to 1J inches. The depressions 
noted in Bulletins Nos. 257 and 407 were not noticeable. 
WEST PALM BEACH, FLA., 1914. 
OIL, TAR, AND OIL-ASPHALT WITH CORALLINE ROCK. 
These experimental sections were constructed about 2 miles south 
of West Palm Beach in May, 1914. The original report giving details 
of materials, methods and traffic, is published in Bulletin No. 257, 
U. S. Department of Agriculture, and supplementary report of con- 
ditions in Bulletin No. 407, U. S. Department of Agriculture. 
The work was inspected on December 11, 1916, and the condition 
of the sections at that time was as follows: 
Experiment No. 1 — Residual asphaltic petroleum, 2.3 gallons, 
penetration method. — This section continued in very satisfactory 
condition. More of the seal coat appeared to be left on the first 
section, station + 00 to station + 50, than on the second section 
of the experiment. A small hole left open at approximately station 
+ 25 is now an irregular opening about 4| by 4J inches and the 
edges show no tendency to travel. Where the seal coat is gone, 
the stone showed a mosaic surface with the exposed aggregate worn 
flat. A wooden block, unintentionally left in the surface near the 
right side at approximate station + 75, and another near the left 
side at approximate station + 85, gave indication of very little 
wear. Seven small pits in the surface were counted near the north 
end of the experiment. Both sections of the experiment would take 
a seal coat of about one-tenth gallon per square yard to advantage. 
Experiment No. 2 — Refined coal tars, 1 .3 gallons, penetration method. — 
A hard, rather than leathery, seal coat was intact on about 60 per 
cent of this experiment, but where breaks occurred there was a 
marked tendency to pit. A block left in the surface at approximate 
station 1 + 79, 2§ feet from the right-hand side, gave indication of 
very little wear. 
Experiment No. 3 — Refined coal tars, 1 .2 gallons, penetration method. — 
This experiment presented a mosaic appearance and showed a pitted 
area approximately three times that noted at the inspection one year 
before. Apparently the tendency to pit was greater in areas where 
excessively large aggregate occurred and possibly also over pockets 
of very fine aggregate or dust. This latter might have been pro- 
duced by the breaking up of large aggregate by traffic and not indi- 
cate fine material in the original construction. From approximate 
