18 BULLETIN 257, U. S. DEPARTMENT OF AGRICULTURE. 
crossing has somewhat increased the surface-repair costs. No re- 
pairs, however, have been large in size. The experiment is in gener- 
ally good condition except for the uniform wear, and it is free from 
holes or weak spots. 
The part of this experiment in Bradley Lane is suffering severely 
by reason of the very heavy traffic in both directions... The frequent 
passing compels practically every vehicle to run off the metal at some 
point, and the continual wear at the edges has reduced the effective 
width and caused damage that can not be satisfactorily repaired short 
of reconstruction. This is an obvious case of the traffic being too 
heavy for a single-line road. : 
EXPERIMENT No. 2 (REFINED WaTER-Gas TaR—Cotp APPLICATION). 
In the early summer of 1914 the surface of this experiment began 
to fail so rapidly through numerous breaks in the mat that it became 
practically impossible to prevent total failure by means of patrol 
maintenance. The failure seemed more pronounced over that portion 
_ of the experiment where gravel had been used, and this is attributed 
to the fact that the gravel was coarser than it should have been. 
Therefore, between June 29 and July 3 a second treatment was 
applied. Refined water-gas tar purchased under the specification for 
the original treatment was used, and the application was made by 
means of an automobile pressure distributor. The tar was brought 
directly from the stills of the manufacturer and applied at a tempera- 
ture of 150° to 175° F, Clean trap-rock chips and g-inch gravel were 
used as a covering material, each over the same parts of the experi- 
ment where it had been originally used. The characteristics of the 
bituminous material are given in the following table, and the cost data 
will be found at the end of this supplementary report. 
TABLE 11.—Analysis of refined water-gas tar. 
ppeenic eravity: 25° /20° O25. . aco ee ee eric ye eee e Een ia eee 1,123 
Wiscosity,, Emeler. 50'c: c. at. 50° ©. specilic. 22°. ie a po ee 
PCR AT DOM! Las ie ob. oS oo ec ie sear ee eee a eee per cent_->, 0580 
Distillation: Sirene ween 
RVenbe ney eceeets UL. cu oe aL cepts eee eee ere ee per cent... 0.0 0.0 
Rasciohtotls to 110° C.. 2. ote eee ee eee dori ee se at 
Second light oils (110°-170° C.)..... SOL Sate ees ee doses 28 5 
Heavyeolss(L70°-270° CO.) 2. css ou. Boake ere ee ee idoz 52 > 4262 phen 
EFeawynoils (2700-315 °C: ) ic). SU ab Meek Sees Lhe do. 222 SS 
Pine herent eee jos 1. . on cee eee ee do. =2. 759 OimGa4 
Pierre Ae gate ee a a eae ee do..-- 100.0 99.9 
This surface is now fully as good, if not better, than at the time of 
original construction. ‘There are two sections of surface, near Nor- 
wood trolley station and south of Edgewood station, where the 
1 Trace solid. 2 One-fourth solid. 3 Fairly hard and glossy. 
a 
