Book IV. 



CARTS. 



431 



with as little injury as possible to the one behind, and by this means make both their 

 powers coincide, two iron fraines are fixed into the axle, in each of which is placed a 

 sheeve or whorl. Upon these sheeves pass a rope or chain (a). In the outside of each 

 shaft is fixed a long iron staple ; and on each staple is placed an iron slider (A), having 

 liberty to shift either forward or backward ; the chain from the collar of the shaft-horse 

 is hooked into the eye of the slider ; and the chain or rope, by which the foremost horse 

 draws, passing from his collar (c), round on the sheeve at the axle, is hooked into the 

 other eye of the slider. By this means the two horses are so connected, that, if the one 

 shall relax, immediately the exertion of the other horse presses the collar hard upon his 

 shoulders, so that he must either exert himself or be pulled backwards. Thus the 

 exertions of the two horses are united, so as to form one power applied to the cart, in 

 place of two powers working generally against one another, which must be the case in 

 the common way of attaching two horses to a cart. But, by this way of yoking, the shaft- 

 horse receives no additional burden from the exertion of the trace-horse, as they both 

 draw from one point, which is the centre of the axle, to the hooks of their respective 

 collars, by which their powers must nearly coincide. If this coincidence does not take 

 place, it is evident that the two horses will, to a certain degree, be pulling against one 

 another, which must be extremely distressing to each in his turn, especially to the one in 

 the shafts. The same principle, as will afterwards appear, has been employed in yoking 

 horses to threshing machines. 



2756. The corn cart has a longer body than the close cart, and the sides and ends are 

 cpen, and support two rails along each. It is made to fit the axle and wheels of the close 

 c^.rt, and is chiefly used in haytime and harvest, when it is supposed to admit of laying 

 o'i\ a larger load of sheaves or hay than the cart and frame. 



2757. Lord Somervilles drag-cart {Jig. 387.) is constructed with a contrivance for 



387 



ZL 



checking or regulating the rapidity of its motion in going down hills or other declivities. 

 The method for adjusting the position of the centre of gravity of the load, and to prevent 

 its pressing too much on the cattle in going down hill, is by a toothed rack, screwed to 

 the front of the cart, and worked by a pinion and handle (a) immediately connected with 

 the pole. By means of this pinion and rack the front of the carriage is elevated more or 

 less, in proportion to the declivity of the hill, by which means the weight of the load is 

 made to bear more on the axis, and less on the necks of the oxen. A friction drag (i) 

 is made to press more or less on the side of the wheel, according to the steepness of the 

 descent ; the one end of it is connected with the tail of the cart by a small chain, and the 

 other end to the front, by means of a toothed rack, which catches on a staple in the front 

 of the cart, by which the pressure of the friction-bar may be regulated at the discretion 

 of the driver : the notches or teeth in this rack, it is observed, should be as close to each 

 other as circumstances will permit. 



2758. The advantages ofthefriction-drag, and other contrivances, are said to be, 1st, The method, which 

 IS equally simple and expeditious, of adjusting the centre of gravity of the load, so as to have a proper 

 bearing on the horses or cattle, in going down hill. 2dly, The method of applying friction to the side of 

 the wheel, to regulate the motion of the carriage in going down hill (instead of locking the wheels), the 

 advantages of which method appear to be as follow : namely, first, the pressure and degree of friction may, 

 with great expedition, be adjusted to the steepness of the declivity, so that the carriage will neither press 

 forward, nor require much exertion to make it follow the cattle ; secondly, the friction is so applied to the 

 wheel, that a given pressure will have twice the efFect in retarding the progress that it would have if 

 immediately applied to the body of the carriage, or to the axis : and, by applying the friction on both sides 

 of the wheel, the risk of heating and destroying the friction-bar is much less than if the same degree of 

 friction were applied in one place. Stily, This apparatus is so conveniently placed, that it can be instantly 

 applied or adjusted, without stopping the carriage, or exposing the driver to the same danger as in locking 

 a wheel. And, 4thly, This contrivance will assume yet a greater importance when applied to both the 

 hind wheels of waggons, by which means the resistance may always be proportioned to the steepness of 

 the descent, the tearing up of the road prevented, the unnecessary exertion of the cattle in drawing the 

 locked carriage down hill avoided, the danger to which the driver is sometimes exposed in locking the 

 waggon-wheel totally evaded, and the time now lost in locking and unlocking the wheel saved to the 

 proprietor. 



