DUST PREVENTION AND ROAD PRESERVATION, 1914. 15 
SUMMARY OF EXPERIMENTS AT WEST PALM BEACH, FLA. 
These experiments were carefully inspected on January 20, 1915, 
and their general condition reported upon as follows: 
Expervment No. 1.—The surface of this experiment throughout is in 
uniformly good condition. The bitumen is still lively and possesses, 
to a certain extent, its original characteristic odor. The flow of the 
excessive bitumen is noticeable here and there along the side of the 
road, but there are no waves or irregularities that would be apparent 
to traffic. 
Experiment No. 2.—The general character of this experiment is 
about the same as that of No. 1, except for its darker color and the 
fact that the bituminous material has become very hard and brittle. 
Experiment No. 3.—The tar used in this experiment has become 
hard and friable. The excess present in the original construction, 
as well as the top dressing of fine rock, has disappeared. The surface 
has worn almost uniformly to a perfect mosaic or terrazzo appear- 
ance, and the large particles of soft rock now exposed are wearing 
very rapidly. A surface treatment will therefore be applied before 
_ any serious wear occurs. 
Experiment No. 4. —This section, while it is in good condition and 
free from any wearing defects, presents a varied appearance. Where 
sand was used there are aise which bear a close resemblance te 
experiment No. 1, while other areas show a mosaic appearance due 
to the wearing of the rock in the wearing course. These differences 
are undoubtedly due to the varied weather conditions under which | 
the experiment was constructed. 
Where rock screenings were used the surface is much lighter and 
somewhat mottled, and evidently more susceptible to wear than the 
sanded surface. 
Experiment No. 5.—This experiment has a mottled appearance due 
to the fact that the bitumen has bled to the surface and formed a 
mat over some areas, while the rock is exposed to wear in others. 
The bituminous spgvaentl | is still lively. 
Experiment No. 6.—This experiment is reported as having been 
somewhat soft and sticky during the summer of 1914, but at the time 
of this inspection it was in excellent condition and presented a smooth 
surface true to the original cross section. 
Experiment No. 7.—This experiment offers an excellent example of 
the relative wear of water-bound coralline rock as compared with 
the bituminous-bound. The surface is smooth, unbroken, and true 
to cross section, but measurements made where it joins the adjacent 
bituminous-bound section indicate that the water-bound macadam 
has worn down about seven-eighths of an inch below the adjacent 
bituminous-bound section. 
93332°—Bull. 257—15——3 
