DUST PREVENTION AND ROAD PRESERVATION, 1914, Oe 
the west half of the section, and there are a number of small worn 
areas in the east half. 
(D) Fluaed native asphalt No. 2 over water-gas tar preparation 
No. 1.—The surface treatment is almost intact on the north half of. 
this section, and the bitumen is still pliable. Over the south half, 
which includes the intersection with Thornapple Street, the surface 
treatment is in general worn off. 
(EK) Fluved natwe asphalt over natiwe asphalt emulsion.—-The surface 
treatment is about two-thirds worn off this section, and the mat 
appears to be rather brittle. 
(F) Oil asphalt No. 1 over water-gas tar preparation No. 1.—The 
surface treatment is almost entirely gone from this section. 
(G) Refined coal tar.—The surface treatment is worn off to a great 
extent over the entire section. 
(H) Water-gas tar preparation No. 2.—The surface treatment is 
still largely intact, although there are quite a number of small areas 
ranging in size from one-half square foot to 1 square foot where it is 
worn off. The majority of these are west of the center line of the 
roadway. 
(1) Fluzed native asphalt No. 2.—On the east half of the roadway 
the surface treatment remains in fairly good condition, but the 
bitumen has become hard, and the surface treatment has disappeared : 
from more than half of the area west of the center line of the roadway. 
(J) Owl asphalt No. 2.—On the west third of this section, adjacent 
to the gutter, the surface treatment is about one-fourth gone, while 
over the remainder it is practically intact, excepting for one worn 
place about 1 square foot in area. Apparently the bitumen still 
possesses life. 
EXPERIMENT No. 4 (O1L-CEMENT CONCRETE) AND EXPERIMENT No. 5 (CEMENT 
CONCRETE). 
No particular difference was noted in the relative wear on the two 
classes of concrete. It is, however, interesting to note the difference 
in wear on the section constructed with trap rock on the grade adja- 
cent to the vitrified brick experiment. The west half of the road, 
which carries the heavy traffic coming up the hill, is worn to an 
appreciably greater extent than the east half. The mortar appears 
to have abraded from around the particles of rock, thus yielding a 
much roughened surface. Over the remainder of the concrete ex- 
periment, extending south from the brow of the hill, the wear has 
been quite uniform over the entire surface. The table following 
shows the distance between cracks when measured on March 10, 1915. 
