DUST PKEVENTIOlSr AN"D ROAD PRESERVATION, 1915. 61 



Section No. 4. — Gilsonite Oil-A.sphalt, Penetration Method. 



The mat on this section is nearly gone and during the summer, 

 especially on the north half of the experiment, heavy patching was 

 necessary. From indications it is probable that similar heavy patch- 

 ing will be required on the south half during the coming season. Dis- 

 integration has appeared along the gutter, due to foundation failure. 

 The mat is decidedly lacking in uniformity, but where the mat is gone 

 the stone is generally well bonded and is wearing smooth, except 

 along the gutters and near the south entrance to the Chevy Chase 

 Club. At this latter point several areas of approximately 1 square 

 foot each are a mass of small cracks, although the mat still covers 

 the stone. These spots are probably evidence of foundation weak- 

 ness. 



Section No. 5. — Oil-Asphalt, Penetration Method. 



On the east side of the car tracks this section is in generally good 

 condition. The mat is becoming very thin, however, especially on 

 that half of the road toward the gutter, and the stone is exposed 

 over large areas; but the aggregate appears well bonded, and the 

 exposed faces are wearing smooth without much tendency to ravel. 

 On the west side, while the road is much more worn and has been 

 heavily patched, especially toward the south end, it is now practically 

 intact, although rough. 



Section No. 6.- — On,- Asphalt, Penetration Method. 



This experiment has the general appearance of section 5. The east 

 side is worn somewhat more evenly than 5, and the stone is more 

 generally exposed, but there is no tendency to ravel. A seal coat 

 should be given in the spring. On the west side the surface is less 

 uniform and is badly pitted and rough for about 50 feet along the 

 gutter near the north end. This is probably due to foundation 

 failure, as mentioned in other sections. The location of this experi- 

 ment was such that at the extreme north end traffic passed over it 

 in almost every possible direction. The main entrance to the Chevy 

 Chase Club, a brick crossover on the suburban trolley tracks, the 

 turnout to Bradley Lane, and the fact that from this point north- 

 ward Kensington Road is surfaced on only one side, while to the 

 south it is surfaced on both sides of the tracks, were conditions that 

 brought such unusual traffic on the extreme end of this section as to 

 wear it very seriously. The adjacent experiment and the brick 

 crossover are much more resistant types of surface than the pene- 

 tration experiment. This contrast is brought out by the fact that 

 over an area of 12 to 15 square yards the penetration experiment was 

 worn from 1 inch to 2^ inches below grade. During the past summer 

 it became necessary to remedy this condition and it was done by 



