DUST PREVENTION AND ROAD PRESERVATION, 1914. 5 
ably reduced. Conditions were generally better than in the other 
experiments of the series. The bitumen (water-gas tar preparation 
No. 2) was heated to an average temperature of 90° C., and applied 
at an average rate of 1.08 gallons per square yard, covered with 
sand, and rolled. | 
EXPERIMENT No. 6 (CaLctumM CHLORIDE). 
In connection with the foregoing series of bituminous experiments, 
- a section of ordinary coralline-rock surface was treated with an 
_ application of calcium chloride, which is a hygroscopic salt obtained 
as a by-product in the manufacture of soda by the Solvay process. 
No record of the cost of this work was obtained. 
The coralline-rock road is at its best when slightly wet or moist, 
and its rapid wear occurs when dry. It was hoped, therefore, that 
the application of a hygroscopic salt in this area bordering on the 
ocean would have the effect of keeping the surface damp, thus secur- 
ing a serviceable and lasting condition. 
Seven drums of calcium chloride, each weighing 350 pounds net, 
were furnished by the manufacturer. Five of these drums were 
-used, the remaining two being reserved for a second application to 
the center of the roadway when necessary. The section which was 
treated on January 28, 1914, lies immediately north of experiment 
No. 1 and is 590 feet long and 18 feet wide, containing an area of 1,175 
square yards. The rate of application was 1.49 pounds per square 
yard, heavy in the center and light on the extreme sides. The mate- 
rial came from the drums in a lumpy condition and was difficult to 
spread evenly. After several weeks of wear the surface was damp 
at all times, but pitted to some extent, showing bare rock in spots. 
SUMMARY OF EXPERIMENTS AT LEMON CITY, FLA. 
When inspected, on January 16, 1915, none of the experiments on 
which bituminous materials were used showed any decided evidence 
of failure. No. 1 appeared to be in slightly better condition than No. 
3, on which the same heated oil had been used. It was fairly smooth, 
had a good cross section, and the bitumen still possessed life. 
Experiment No. 2, where the light oil was used, was in good con- 
dition, but the bitumen had a brownish, dead appearance, and the 
individual rock particles showed throughout the section. 
Experiment No. 4, which received the double surface treatment, 
showed a fine-grained mosaic surface with a few incipient potholes. 
It had not worn appreciably below the adjacent section. 
Experiment No. 5 had a perfect mosaic surface, with slight indenta- 
tions around the individual particles of stone. The bitumen had 
become quite hard, and the section should be given a light surface 
treatment at an early date. One depression was noted in this experi- 
ment, on the west side, at the joint about 55 feet from the south end. 
