6 BULLETIN 407, U. S. DEPARTMENT OF AGRICULTURE. 
scarified and reshaped with some difficulty, as the left edge from 
station 221+00 to station 230 + 00 was 3 inches higher than the 
crown. From station 201 + 00 to station 208 + 89 and from station 
215 + 28 to station 219 + 00 the old macadam was entirely removed 
to correct the profile and a new subgrade constructed. Six inches 
of "li-inch" crushed granite (passing a 2|-inch screen and retained 
on a lj-inch screen) was then placed. It was also necessary to add 
such stone to weak spots in the base between station 229 + 00 and 
station 234 + 00. The entire base was rolled with a 10-ton macadam 
roller. A gap of 639 feet occurs on this section at the viaduct over 
the Potomac railroad yards. 
Shoulders. — Earth shoulders on Section I were constructed 4 feet 
wide with a slope of 1 inch to the foot, and they were finally trimmed 
and rolled upon completion of the work. On Section II 4-foot gravel 
shoulders of approximately 4 inches of compacted gravel from the 
Haney pit were constructed on both sides throughout the entire 
length. On Section III, from station 219 + 00 to station 235 + 50 
similar gravel shoulders were constructed on both sides, except 
where a sufficient amount of material developed in the course of 
reshaping the old macadam with which to form a firm shoulder. 
Cut-off. — Near station 2 + 50 a branch (or cut-off) was built for a 
distance of 230 feet along the southerly branch of the Washington- 
Virginia Railroad to allow traffic to pass through the new road and 
reach the Military Road going to Georgetown without twice crossing 
the railroad track. The surface of this cut-off was constructed as 
parts of experiments Nos. 1 and 2. 
Right of way. — Approximately 10.2 acres of land were acquired by 
Alexandria County to provide for widening the old road and for the 
new right of way. All lands so acquired are marked at every point 
of curvature and tangency along the new right of way by means of 
concrete monuments. 
Curves. — The reverse curve between stations 34 + 07 and 37 + 75 
was widened gradually to a total width of 24 feet and suitably banked. 
The curve between stations 84 + 10 and 88 + 76 was widened grad- 
ually to a total width of 22 feet, and also suitably banked. The 
curve between stations 89 + 73 and 93 + 99 was also widened gradu- 
ally to 22 feet. 
Guard rail. — Wooden guard rails were constructed on Section I 
as follows : 
From station 19+20 to station 34, left. 
From station 20+26 to station 22+55, right. 
From station 73+80 to station 81+64, right. 
From station 74+24 to station 78+70, left. 
From station 91+50, 3 panels on the right. 
From station 98+70 to station 108+78, both sides. 
At Hume Spring 4 panels of guard rail were erected. 
