20 BULLETIN 257, U. S. DEPARTMENT OF AGRICULTURE. 
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 suriace 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 (Resipuat ASPHALTIC PETROLEUM—Hor 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 (Resmpuat AspHALTIC PETROLEUM—HortT 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. 
