BULLETIN 691, U. S. DEPARTMENT OP 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. 



