4 BULLETIN 53, U. S. DEPARTMENT OF AGRICULTURE. 
BITUMINOUS-MACADAM ROAD. 
Silver Spring. Md. — The seal coat was renewed on the bituminous-macadam 
drive extending from Silver Spring station to the Blair estate, the construction 
of which was supervised by the Office of Public Roads during the year 1912 and 
described in its annual report for that year. Work was begun on June 27, 1913, 
and completed on July 1, 1913. The road is 2,776 feet in length and 12* feet wide, 
making a total area of 3,856 square yards. The road surface was first thor- 
oughly cleaned with stiff brooms, after which a total of 1.075 gallons of a light 
water-gas tar preparation was applied to the road directly from the drums at 
the rate of approximately 0.28 gallon per square yard. This material was then 
distributed by means of hand brooms so as to form a uniform coating over the 
entire surface. Sixty-six tons of pea gravel were spread over the bituminous 
material at the rate of approximately 0.0133 cubic yard per square yard. The 
surface was then lightly rolled with a 10-ton macadam roller. 
Several water-bound macadam patches, aggregating 100 square yards in area, 
were made. Seven and one-fourth cubic yards of crushed limestone and 4£ 
cubic yards of limestone screenings were used for this purpose. 
The entire cost of renewing the seal coat was $283.78, while the patches cost 
$40.07. The cost of the road per square yard for the seal coat was $0.0736. 
The principal items of cost were as follows: Bituminous material, delivered 
at the station, 1,075 gallons, at $0,095 per gallon, $102.13; loading and haul- 
ing the bituminous material to the road, $12.55; pea gravel, delivered at the 
station, 6G tons, at $1.20 per ton, $79.20; loading and hauling the gravel to 
the road, $7.05; sweeping the road surface, $8.33; applying the bitumen. $23.83; 
spreading the gravel, $11.50; rolling, $23.65; limestone for patching the mac- 
adam, 11£ cubic yards, at $2 per cubic yard, $23; labor for patching the 
macadam, $25.57; coal for the roller, $3.50; and general expenses, $12.50. The 
above costs are based on labor at $1.60 and teams at $4.75 per nine-hour day. 
MACADAM ROADS. 
Black Rock, Ark. — Work was begun on a macadam road extending from 
Black Rock westward toward Smithville on September 25, 1912, and discon- 
tinued for lack of funds on October 26, 1912, with the loss of 1£ days on 
account of bad weather. 
The land adjacent to the road is hilly, and the natural soil is clay. The road 
was graded 30 feet wide in cuts and 20 feet wide in fills for 2,600 feet, making 
a graded area of 7,500 square yards. The maximum cut was 3£ feet, the maxi- 
mum fill 3 feet, and the total amount of excavation 2,620 cubic yards. Earth 
was loosened with plows, hauled with drag and wheel scrapers, and spread by 
haDd and with a road grader. The average haul for excavation was 75 feet and 
the maximum, 300 feet. 
A surface of macadam was laid for 1,300 feet, 12 feet wide, making 1,733 
square yards. For 660 feet the macadam was applied in two courses, each 5 
inches thick at the center and 4 inches at the sides before compacting, and 
throughout the remaining 640 feet it was applied in one course. In both in- 
stances the material was compacted 8 inches at the center and 6 inches at the 
sides. The material used for surfacing was a hard magnesian limestone with 
good binding qualities. The run of the crusher was used for both the first and 
second courses; and the maximum size in the first course was 4 inches and in 
the second course 2£ inches. " Chats," or the tailings from a zinc mine, were 
used as a binder in an amount just sufficient to bind the surface properly. This 
material was similar to that used for surfacing. It ranged in size from one- 
