DRY FARMING CONGRESS. 



121 



to the cost of construction. A grade may be so steep as to limit the 

 size of load that can be moved over the road, thereby making it necessary 

 to carry smaller loads than otherwise would be required. 



The Power of a Horse on the Road. 



A horse, with reasonably good footing, can exert a pull equal to 

 one-tenth of his weight, at a speed of two and a half miles per hour, 

 for ten hours per day, for six days per w^eek, and keep in good condition. 

 At this rate a thousand pound horse would exert but two-thirds of a 

 horse power and a 1,500-pound horse would exert one horse power. The 

 maximum draft of a horse is about one-half his weight; he can exert 

 this much energy at a slow walk for a distance not to exceed 100 feet. 

 At this rate he would develop energy enough for ten hours, in two hours' 

 time. A horse can exert a draft equal to one-fourth of his weight and 

 stand it for a much longer time. Then the working tractive power of 

 a horse may be taken as one-tenth his weight, w4th an ordinary maxi- 

 mum of one-fourth, and in great emergencies a maximum of one-half 

 his weight. According to Baker, it requires a tractive force of 100 

 pounds to move one ton of load over an ordinar^^ level earth road. A 

 team of 1,200 pounds each, pulling at the rate of one-tenth their weight, 

 would be able to pull 2.4 tons on the level. Pulling at the rate of one- 

 fourth their weight, this team would be able to pull this same load up 

 a five per cent grade, and would probably be able to pull it 400 or 500 

 feet. This load pulled by the same team exerting a pull equal to one- 

 half their weight could just be moved up a twelve per cent grade for a 

 short distance only. Thus we see that if there was a short, steep, twelve 

 per cent grade on a certain road, the largest permissible load that could 

 be carried over the road with a team of 1,200 pounds each, would be 

 2.4 tons. 



According to Gillespie, "It costs one and one-half times as much 

 to haul over a road having a five per cent grade, and three times as 

 much over one having a ten per cent grade as on a level grade." 



Care of Earth Roads. 



The work of maintaining an earth road is largely that of keeping 

 the drainage system free from obstruction, and the surface smooth. 



Outlets to tile drains should be examined frequently. Trash which 

 may have been collected at the mouth of the tile should be removed. 



Side ditches must be kept open and free from w^eeds. Where the 

 sides begin to wash badly they should be protected with stone, brick, 

 plank, or tile, and should not be allowed to wash deeper or wider than 

 is necessary. 



Traffic over any road has a tendency to wear the surface of a road 

 unevenly. For this reason it is necessary to provide some means for 

 keeping the surface smooth, thus keeping out the w^ater. If this is not 

 done, as soon as ruts are formed, the water will stand in them and soften 

 the surface and in a short time the road is nearly impassable if not en- 

 tirely so. 



