162 FARM ARITHMETIC. 



Important truth. It should be remembered that when 

 the driver rides on the disk harrow, more useful work is 

 done, since more soil is moved. Thus while draft is in- 

 creased, the work is not necessarily uneconomically done. 



Oral Problems on Draft of Disk Harrows. 



563. When the -disk harrow is set at full angle about 

 how many horses are necessary? About what weight 

 should they be ? Should they be worked continuously and 

 at rapid gait ? About how fast should they walk ? 



564. When set at angle as ordinarily used, how many 

 horses may be used ? Their weight ? How rapid gait ? 



565. How does the draft of the disk harrow compare 

 with the draft of the plow ? 



Spring-Tooth Harrow. 



566. When the spring-tooth harrow is set so as to cut 

 4 inches deep the total draft is 451.3 pounds. How many 

 1,200-pound horses are needed when they are expected to 

 work steadily all day and walk two miles each hour ? 



Corn Binder. 



The following shows the draft of the corn binder. 



567. How many pounds more of draft are required 

 by heavy corn than by light? 



568. What is the percentage of difference? 



