Influence of Grade on Draft. 431 



the better the level part of the road, the longer the haul 

 and the more teams to pass over it, the less steep should the 

 grade be. On all well designed roads a great effort is 

 usually made to keep below a rise of seven feet in 100 feet. 



Just why low grades are so necessary will be readily 

 understood from the following considerations : 



About the maximum walking draft of a horse on a good 

 level road is measured by one-half his weight. Trials have 

 shown that a 1,634-lb. horse can exert a steady pull of 

 800 Ibs. while walking 100 feet, and that an 836-lb. horse 

 may maintain through the same distance a steady draft of 

 400 Ibs. It would not be safe, however, to repeat such 

 strains often nor maintain them long. Even a draft equal 

 to one-fourth the weight of the animal is a heavy and ex- 

 haustive pull. Indeed a steady pull equal to one-tenth of 

 the weight of the horse for a ten-hour daily service at the 

 walking pace of 2.5 miles per hour is an average of effect- 

 ive service and the work of a 1,000-pound horse would 

 equal 



60X33,000 



Taking this as the safe rate of work for a team on the 

 road an 800-pound horse may pull steadily 80 Ibs. ; he may 

 pull over hills at the rate of 200 Ibs. and in emergencies 

 400 Ibs. A 1,600-pound horse at the same rating may 

 pull steadily 160 Ibs., up hills 400 Ibs. and in an emergency 

 800 Ibs. 



It has been found that to move a gross ton over a good 

 level dirt road requires a traction of about 140 Ibs. A 

 team of 800-pound horses may therefore come to a hill with 

 a load of 



JQ tons = 2,285$ pounds. 



Up how steep a grade may such a team carry this load 

 with a steady exertion of 200 Ibs. per horse? To over- 



