442 Farm Mechanics. 



struction, it will be found that the "draft decreases until 

 this direction is reached, but that passing beyond it again 

 increases. In other words, the draft is least when the di- 

 rection of the traces is parallel with the effective road-bed. 



It is clear, therefore, that in teaming with wagons on 

 the field and on any but rigid, smooth roads the least draft 

 is secured when the traces incline more or less downward, 

 the amount increasing the more yielding and the more un- 

 even the road. 



In regard to the division of the load between the front 

 and hind wheels it is clear that the hind wheels are drawn 

 by the reach from the king-bolt, the line of draft being 

 nearly horizontal, and, this being true, it may fairly be 

 concluded that on ordinary roads and upon the field the 

 load must draw harder if the heaviest portion is not placed 

 upon the front wheels where the line of draft can be more 

 inclined. It is quite possible and even probable that when 

 the unevenness of the road is considerable the least draft 

 may be secured when the front wheels are carrying more 

 than half the load. More observations, however, are re- 

 quired along this line to establish the whole truth. 



543. Bigidity of the Carriage. Where the road is not per- 

 fectly smooth and where the speed is faster than a medium 

 walk, springs under the load diminish the draft and the ad- 

 vantage of elasticity increases with the roughness of the 

 road and with the speed. For small and rigid inequalities 

 in the road the maximum advantage is secured in the use 

 of the elastic tire, and especially with the pneumatic form, 

 where the load is not too heavy, because in these cases 

 the energy which would be lost by concussion is prevented, 

 the tire quickly and effectually conforming to the road. 

 Where the loads must be heavy, and where the inequalities 

 are larger, then springs under the load carried by the axles 

 respond in rapid transit and relieve the concussions and 

 thus lessen the draft, diminish the strain upon the car- 

 riage, and permit less injury to the road. 



