477 



594. Revolving Screen. Th - revolving sen en is an indis- 

 pensable attachment to a rock crusher, becau>e ;i n>.id road 

 cannot bo made with the nnss-rted material, for with this 

 method of putting the crushed rock H]>MH the mad the fine 

 materials are certain to work downward and the coarser 

 fragments to come to the surface. It should be thoroughly 

 understood too that the chute screen will not do the work 



FIG. 228. Side view of No. 3 Austin Crusher and wagon loading screenings. 



595. Earth and Stone Road Combined. Where it is de- 

 sired to cheapen the construction of stone roads it is prac- 

 ticable to make the central portion 8 feet wide of this ma- 

 terial and then have on one or both sides an earth road 

 of eight feet, giving a total width of 1C or 24 feet to the 

 margin of grass and .>0 feet to the side ditches. The most 

 serious objection to tlii< combined plan is ;he securing at 

 all times of sufficient and quick surface drainage. 



The chief difficulty which will arise in the carrying out 



