424 AGRICULTURE 



this rule must often give way to avoid the climbing of too 

 heavy grades. 



Straightness and grade. To lift a ton one foot high 

 requires two thousand foot-tons of energy. On a road sur- 

 face requiring one hundred pounds traction per ton, the 

 same energy would roll the ton a horizontal distance of 

 twenty feet. As far as the actual amount of energy used is 

 concerned, therefore, to save one foot of grade, or up-hill 



Eurth road in Kansas. 



climb, the road may be lengthened twenty feet. Public 

 road grades should avoid a rise of more than >i.\ feet in a 

 distance of one hundred feet. The hills should be cut down 

 and the material used to fill in the hollows or else the road 

 relocated to go around the hill and to avoid the steep grades. 

 The necessity of sunlight. Every road bed should 

 have at least six hours of sunlight each day. Brush, trees 

 or hedges that interfere with this requirement should be 

 cleared away or sufficiently thinned out. On the other hand, 



