POWER EEQUIRED ON DIFFERENT ROADS. 243 



To take an example, suppose we have a truck weighing with 

 its load 9,000 lbs. How many pounds traction will be required 

 to 'move the same ? 



Ans. — On jfirm soil, gravel 4"-6" deep, that is, a newly repaired 

 road, as we often find it, (^ by table,) 1,000 lbs. ; on best kind 

 of embankment, (^^ by table,) 310.3 lbs. ; on broken stone road 

 in good condition, (^^^ by table,) 166.6 lbs. ; on broken stone 

 road, deep ruts and mud, (J^ by table,) 643. lbs. ; on a good 

 pavement, (gig by table,) 138.5 lbs. Or, since the tractive force 

 of a medium horse when working all day is said to be about 125 

 lbs., we need in the first case, 8 horses ; in the second case, 2^ 

 horses ; in the third case, about l^^ horses ; in the fourth case, 

 about 5 horses ; and in the fifth case, only one good horse to 

 move the same entire load all day. 



