BULLETIN 691, U. S. DEPARTMENT OF AGRICULTURE. 
from one-third to one-half gallon per square yard. It should be 
covered with a uniform layer of dustless broken stone all of which 
will pass a one-inch or three-fourths inch laboratory screen or 
pea gravel which will pass a one-half inch laboratory screen in 
an amount just sufficient to absorb the bitumen and to prevent the 
surface from picking up under traffic. Subsequent applications 
may be made by a pressure distributor or by brooming the oil 
uniformly over the road surface. From one-tenth to one-fifth 
gallon per square yard will usually prove sufficient, and this 
should be covered with coarse sand or stone chips which will pass 
a one-half inch laboratory screen. To obtain best results the 
treatment should be applied in the early summer except in locali- 
ties where snow and freezing weather are not common. Under 
favorable conditions with occasional patching of any breaks 
in the surface a treatment should last for several years. 
