20 BULLETIN 257, U. S. DEPABTMENT OF AGBICTJLTTJEE. 



At the date of inspection this experiment was in essentially as good 

 condition as at the time of construction. The surface was noticeably 

 better on the gravel half of the section and had a corky feeling to the 

 tread throughout. In wet weather the surface has become somewhat 

 muddy, especially in the bottoms, and this action appears character- 

 istic of all the experimental surfaces treated with petroleum products. 



In deducing maintenance costs for this section, proper allowance 

 has been made by excluding the cost of subsurface repairs not due to 

 failure of the surface treatment. 



Experiment No. 4 (Residual Asphaltic Petroleum — Hot Application). 



This experiment presented probably the best appearance of any of 

 the original construction at the time of last inspection. During the 

 winter of 1913-14 its surface remained practically intact, but in the 

 winter of 1914-15 it cracked in a few places and became slightly 

 muddy. The muddy condition rapidly disappears in dry weather 

 and a smooth leathery surface results. 



The surface has had about the same amount of attention as that of 

 experiment No. 1, and will probably not require a general re-treat- 

 ment during the coming season. This experiment, together with 

 No. 5 and No. 6, all of which were given hot surface treatments, 

 required considerable top-dressing during the first warm days of 

 spring to stop further bleeding. The surface still has a few humps 

 in spots where the distributor leaked at the time of spreading the 

 bitumen. Many of these humps have been cut down with a mattock 

 or hot shovel, but all are not yet entirely removed, because their 

 tendency to bleed and consequent addition of top-dressing tend to 

 build them up again. Three or four potholes were noted, and at one 

 place on the east side of the road there appears to be a stripped track 

 that has developed since the late fall of 1914. This may have been 

 a long repair made at the time of construction after an automobile 

 ran over the section before top-dressing was spread. Along this strip, 

 some 500 or 600 feet in length, and between it and the edge of the 

 surface the underlying macadam is generally bare, but is not raveling. 



Experiment No. 5 (Residual Asphaltic Petroleum — Hot Application). 



The surface shows a tendency to crack in cold weather, and in wet 

 weather works into a mud more readily than the surface of experi- 

 ment No. 4. Like experiment No. 4, the surface is soon ironed into a 

 smooth, leathery mat when dry weather permits. During the year 

 the cost of surface work has been greater than on No. 1 or No. 4. It 

 was also slightly higher than on No. 6. The hilltop at the north end 

 of the experiment is better than elsewhere, probably on account of 

 more thorough subdrainage. Any areas poorly drained are at once 

 noticeable through this surface. 



