so MECHANICS. 



eight yards, or one twelfth of a mile longer. The same 

 steep hill is ascended perhaps fifty to five hundred times 

 a year by a hmidred different farmers, expending an 

 amount of strength, in the aggregate, sufficient to ele- 

 vate ten thousand tons annually to this height, as a 

 calculation will at once show — more than enough for 

 all the increased expense of making the road level. 



It is interesting and important to examine how 

 much further it is expedient to carry a road through 

 a circuitous level course than over a hiU. To ascer- 

 tain this point, we must take into view the resistance 

 occasioned by the rough surface or soft material of the 

 road. Roads vary greatly in this particular, but the 

 following may be considered as about a fair average. 

 In drawing a ton weight (including wagon) on freely 

 running wheels, on a perfect level, the strength exert- 

 ed will be found about equal to the following : 



On a hard, smooth plank road 40 pounds. 



On a good Macadam road 60 " 



On a common good hard road 100 " 



On a soft road about 200 " 



Now let us compare this resistance to the resistance 

 of drawing up hill. First, for the plank road — forty 

 pounds is one fiftieth of a ton ; therefore a rise of one 

 foot in fifty of length will increase the draught equal 

 to the resistance of the road. Hence the road might 

 be increased fifty feet in length to avoid an ascent of 

 one foot ; or, at the same rate, it might be increased a 

 mile in length to avoid an ascent of one hundred and 

 five feet. But in this estimate the increase in cost of 

 making the longer road is not taken into account. If 

 making and keeping in repair be equal to three hund- 



