ASCENT IN ROADS. 87 



high will attain a speed of 96 feet per second, or more 

 than 65 miles an hour, at the foot of the plane, which 

 is equal to the velocity of a stone falhng three seconds, 

 or 145 feet. 



ASCENT IN ROADS, 



All roads not perfectly level may he regarded as in- 

 chned planes. By the application of the preceding 

 rule, we may discover precisely how much strength is 

 lost in drawing heavy wagons up hill. If the load 

 and wagon weigh a ton, and the road rise one foot in 

 height to every five feet of distance, then the increased 

 strength required to draw the load will be one fifth of 

 its weight, or equal to 400 pounds. If it rise only one 

 foot in twenty, then the increase in power needed to 

 ascend this plane will be only 100 pounds. The great 

 importance of preserving as nearly as practicable a per- 

 fect level is very obvious. 



There are many roads made in this country, rising 

 over and descending hills, which might be made near- 

 ly level by deviating a little to the right or to the left. 

 Suppose, for example, that a road be required to con- 

 nect the two points a and b {Fig: 70), three miles 



Fig. 70. 



^^i^^^^^.A'n^if. ,,-i 



apart, but separated by a lofty hill midway between 

 them, and one mile m diameter. Passing half a mile 

 on either side would entirely avoid the liill, and th& 

 road thus curved would be only one hundred and forty- 



