ON RAISING AND REMOVING WEIGHTS, 210 



turned with great ease. In particular situations, these waggons are 

 loaded by little carts, rolling without direction down inclined planes, and 

 emptying themselves; they are also provided with similar coutrivcnces for 

 being readily unloaded, when they arrive at the place of their destination. 

 The carriages used for drawing loaded boats over inclined planes, where they 

 have to ascend and again to descend, are made to preserve their level by 

 having at one end four wheels instead of two, on the same transverse line; 

 the outer ones as much higher than the pair at the other end, as the inner 

 ones are lower; and the wheelway being so laid, that either the largest or tlie 

 smallest act on it, accordingly as the corresponding part of the plane is lower 

 or higher than the opposite end. It is possible that roads paved with iron 

 may hereafter be employed for the purpose of expeditious travelling, since 

 there is scarcely any resistance to be overcome, except that of the air, and 

 such roads would allow the velocity to be increased almost without limit 



For removing earth from one situation to another, a series of baskets has 

 sometimes been hung on two endless ropes, moving on pullics of such a form, 

 as to suffer the bars supporting the baskets to pass freely over them ; the 

 baskets being moved by means of a winch, acting on the rope by a wheel 

 like one of the pullies. Sometimes also a series of httle carts has been con- 

 nected by ropes, and drawn in a circle or oval up and down an inclined plane. 

 These methods may be adopted in making roads, where a hill is to be levelled, 

 and the materials are to be employed in filling up the valley below: but in 

 such cases two carts, connected by a cylinder or windlass, are generally 

 sufficient; and they may be arranged in the same manner as the carriages for 

 removing boats on an inclined plane. 



