24 



BULLETIN 463, U. S. DEPARTMENT OF AGRICULTURE. 



very tenacious it should be harrowed with a disk harrow (fig. 13) 

 ahead of the grading machine, and after the material has been 

 moved over toward the center of the road the lumps of sod should be 

 thrown out. A method sometimes followed is to skim off the sod, 

 by means of hand shovels, ahead of the grading machine, but this 

 method is expensive and seldom justified. 



Whether or not it is necessary to contend with any considerable 

 quantity of sod, the use of a disk harrow usually will prove helpful 

 in securing a smooth uniform road surface with the grading machine. 

 In general it is sufficient to give the loosened material a thorough 

 harrowing after the road has' been brought approximately to it? 



required shape, but 

 before the final shap- 

 ing is done. 



Where continuous 

 long stretches of road 

 are to be graded with 

 grading machines, it 

 frequently is econom- 

 ical to substitute a 

 traction engine for 

 the teams and to em- 

 ploy two machines. 

 Where this is done 

 the first machine is 

 connected immedi- 

 ately behind the trac- 

 tor, either directly 

 behind or to one side, as the conditions require, and the second 

 machine is connected behind and to one side of the first. Otherwise 

 the method of operation is not essentially different from that already 

 described. 



The rate at which a road can be graded up with a grading machine 

 varies to a great extent, and depends largely on the character of 

 the soil. Where the original cross section of the ground is approxi- 

 mately level, such as that shown in the model (PL II), the cross 

 section of the finished road similar to that shown in figure 12, and 

 the soil conditions not unfavorable, a grading machine drawn by six 

 well-trained horses should cut out the side ditches and shape the road 

 in from 20 to 35 round trips. Allowing for a reasonable amount 

 of lost time, the rate at which the team travels should average from 

 1^ to 2 miles per hour, and under the circumstances assumed above, 

 the length of road graded per day should average not less than 

 one-fourth mile. Such favorable conditions seldom are found for 

 any considerable stretch of road, except in the prairie sections of the 



Fig. 13. — Breaking up clocls with a disk harrow. 



