BULLETIN 691, U. S. DEPARTMENT OF AGRICULTURE. 
fourths-inch laboratory screen, or with pea gravel, which will 
pass a one-half-inch laboratory screen in an amount just suffi- 
cient to absorb the bitumen and to prevent the surface from 
picking up under traffic. Subsequent applications may be made 
by a pressure distributer 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 clips which will pass a one-inch laboratory 
screen. 
To secure best results the treatment should be applied in the 
early summer, excepting in localities where snow and freezing 
weather are not common. Under favorable conditions a treat- 
ment should last throughout at least one season. 
G 
