DUST PREVENTION AND ROAD PRESERVATION, 1915. 61 
Section No. 4. — Gilsonite Oil- Asphalt, 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. — Oil- 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 
