Stone Roads. 473 



the stone again begin to move. This is most likely to oc- 

 cur when the stone is too dry. , 



591. Manner of Rolling. The rolling should begin at (lie 

 outer sides of the road, packing the stone tirst against the 

 shoulder. If this is not done the fact that the road-bed 

 is highest in the center will lead to flattening the slope and 

 thinning out the rock in the center through a side creeping 

 of the material from under the roller. 



592. Kind of Roller. There are three methods of consol- 

 idating the layers of stone put into a road. The tirst, now 

 largely abandoned as being too expensive and too uncertain, 

 is to allow it to be done by the natural traffic. The second, 

 also being abandoned as too expensive, is the use of a 3.5 

 to 5-ton horse roller ; and the third, which is regarded the 

 cheapest and best, is with the aid of an 8 to 20-ton steam 

 roller. 



The safest indications seem to point to the use on coun- 

 try roads of an 8 to 10-ton steam roller as most satisfactory ; 

 although good work can be done with the horse roller of 

 half this weight which may be made heavier or lighter by 

 taking on and laying off weights Such a roller as this 13 

 represented in Fig. 226 which, naked, weighs 3.5 tons, 

 but by the addition of castings to the inside of the roller 

 may be increased to 5.5 tons. This roller has the frame 

 and tongue so constructed that the team may be turned 

 without reversing the roller, a very important feature. 



It will be readily seen that the use of two men and two 

 teams must make the service of this roller very expensive, 

 and when the disturbing effects of the horses' feet are re- 

 called it becomes clear that the steam roller easily managed 

 by one man is much better. 



593. Rock Crushers. Until recently all rock crushing for 

 road work has been done by hand and hammer, and in the 

 days of slave labor when the man was a machine which 

 managed, fed, cared for and reproduced itself, it is clear 



