DUST PREVENTION AND ROAD PRESERVATION. 31 



throughout the most traveled area. The oil was applied in the same 

 manner as on the two previous sections and covered with torpedo 



The east arm of the fork at the north end of the section was not 

 treated at this time, owing to the fact that traffic through there 

 had not been sufficient to crush the gravel covering completely. 

 The surface treatment, however, had by winter disappeared over an 

 area of about 4 square yards, and in December this place was patched 

 with a surface application of oil and fine gravel. 



The total cost of maintaining this section was $27.45, or 2.08 cents 

 per square yard, for the entire section. When last inspected it 

 presented a smooth, uniform surface throughout. 



SUPPLEMENTARY REPORT OF EXPERIMENTS AT CHEVY CHASE, MD., 



1911 PROJECT. 



BITUMINOUS CONSTRUCTION AND SURFACE TREATMENT. 



The original reports of these experiments are given in Circulars 

 Nos. 98 and 99. The following report is based upon an inspection 

 made January 29, 1914: 



Section No. 1. — Refined coal tar — Penetration method. 



The surface of this section is well bound and presents as a whole a 

 satisfactory appearance, but the seal coat is worn off to the extent 

 of about 75 per cent and a few shallow, worn depressions can be 

 noted. It was decided that a new seal coat was not necessary at the 

 beginning of the past season, but an application of a light tar and 

 screenings will very likely be made in the spring. 



Section No. 2. — Refined coal tar — Modified Gladwell method. 



The surface of this section is well bound and its general appear- 

 ance is good excepting for a slight unevenness. This is to be ex- 

 pected from the excessive bleeding which originally took place and 

 the necessary irregularity in the distribution of chips to take up the 

 bitumen. 



Section No. 3. — Fluxed native asphalt — Penetration method. 



This section continues to present an excellent appearance. The 

 seal coat as a whole is intact excepting for a few small areas which 

 present a somewhat mosaic appearance. No holes or depressions 

 are in evidence and the section has had no repairs to date. 



Section No. 4. — Gilsonite oil asphalt — Penetration method. 



As a whole this section continues in good condition and, excepting 

 for a slight unevenness, the surface presents a satisfactory appear- 

 ance. There are, however, a few places where the coarse stone shows 



