HIGHWAY CONSTRUCTION 



in form according to the kind of work they are intended for, viz.: 

 loosening earth, gravel, hardpan, and some of the softer rocks. 



These ploughs are made of great strength, selected white oak, 

 rock elm, wrought steel and iron being generally used in their con- 

 struction. The cost of operating ploughs ranges from 2 to 5 cents 

 per cubic yard, depending upon the compactness of the soil. The 

 quantity of material loosened will vary from 2 to 5 cubic yards per 

 hour. 



Fig. 31 shows the form usually adopted for loosening earth. 

 This plough does not turn the soil, but cuts a furrow about 10 



Fig. 31. Grading Plow. 



inches wide and of a depth adjustable up to 11 inches. 



In light soil the ploughs are operated by two or four horses; in 

 heavy soils as many as eight are employed. Grading ploughs vary 

 in weight from 100 to 325 Ib. 



Fig. 32. Hardpan Plow. ' 



Fig. 32 illustrates a plough specially designed for tearing up 

 macadam, gravel, or similar material. The point is a straight ba.r 

 of cast steel drawn down to a point, and can be easily repaired. 



