DUST. PREVENTION AND ROAD PRESERVATION. 41 
SUPPLEMENTARY REPORT OF EXPERIMENT MADE AT BOISE, IDAHO, 
1910. 
OIL-GRAVEL MACADAM. 
The original report of this experiment was published in Circular 
No. 94 and reports of annual inspections were given in Circulars Nos. 
98 and 99. The following report covers an inspection made on April 
25, 1914: 
The south or wide section of the road, which is the portion described 
in Circular No. 94, was practically all in the same condition and con- 
tained a number of potholes. There was, however, no indication of 
surface disintegration at any point throughout the entire construction. 
The narrower portion contained a few ruts, but generally speaking it 
was in fairly good condition. A new flush coat of bituminous mate- 
rial would undoubtedly prove beneficial on some stretches. From 
the cemetery eastward for a distance of about 1,900 feet the road had 
just been given a flush coat of a fairly heavy asphaltic petroleum 
product and had been covered with good coarse sand and fine gravel. 
Such ruts and depressions as had developed from time to time are in 
all probability due to the poor foundation, which was noted in the 
original description of the experiment. 
SUPPLEMENTARY REPORT OF EXPERIMENT MADE AT AMES, IOWA, 1910. 
OIL-ASPHALT GRAVEL. 
The original report of this experiment was published in Circular 
No. 94, and reports of annual inspections were given in Circulars Nos. 
98 and 99. The following report covers an inspection made on 
January 7, 1914: 
The general condition of the section is good, although it was 
covered with a layer of dust from one-fourth inch to three-fourths 
inch in thickness. The shape is well preserved, excepting for two or 
three depressions, and the wear has not been excessive. The surface 
in general resembled a brown layer of packed gravel and old bitumin- 
ous material which is "short" and friable. 
SUPPLEMENTARY REPORT OF EXPERIMENTS MADE AT KNOXVILLE, 
TENN., 1910. 
TAR AND OIL PREPARATIONS. 
The original report of these experiments was published in Circular 
No. 94, and reports of annual inspections are given in Circulars Nos. 
98 and 99/ The following report is based upon an inspection made 
on December 17, 1913, during a period of cold, damp weather: 
