214 



ENGINEERING ON THE FARM 



should elapse between the end of the rain and the dragging 

 will depend upon the material of road surfacing. Surfaces 

 that contain sand can be worked much sooner than those 

 largely clay. Some experimental work is required on each 

 road for determining the time that will give the best rssults. 

 The man employed to do the dragging should be so situated 



"mm 



Fig. i 86. Use of the King road drag 



that he can get on the road at the proper time, and he 

 should not have the care of a larger section than he can pass 

 over within reasonable time limits. 



The principle on which road dragging benefits the road 

 is that of puddling the soil. Any soil containing clay 

 becomes tough and impervious to water with working and 

 tamping while wet. Low places in barnyards hold water 

 even though underdrained, owing to the tramping of stock 

 which causes puddling. The use of the road drag on the 

 wet road is the application of this same principle. The 

 drag fills up all tracks and ruts, and the traffic then packs 

 it. One of the objects of the drag is to obliterate all tracks 



