DUST PREVENTION AND EOAD 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: 



Experiment 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 places which bear a close resemblance to 

 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 material 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 

 hit ominous-bound eel ion. 

 93832°— Bull. 267 -16 3 



