400 



SCIENCE OF AGRICULTURE. 



Part II. 



than the one in the shafts, which may frequently loappen ; and by this means, a still 

 greater burden is laid upon the back of the horse employed in the shafts. 



2613. Improved tioo-harse carts f^. 342.). It may be suggested to those who are 



fond of employing two-horse carts, that in order to adjust the traces of the fore horse 

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

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

 sheeve or whorle. 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 (5), 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 tlie 

 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 ex- 

 ertion 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. 



2614. The corn cart has a longer body than the close cart, and the sides and ends are 

 open and supf>ort two rails along each. It is made to fit the axle and wheels of the 

 close cart, and is chiefly used in haytime and harvest, when it is supposed to admit of 

 laying on a larger load of sheaves or hay than the cart and frame. 



2615. Lord SomervUle s drag-cart {Jig. 343.) is constructed with a contrivance for 



343 



ZZD 



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 pre- 

 vent 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 () 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 (J) 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 friction-bar may be made to press on the side of the wheel, 

 more or less, 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. 



2616. Tlie advantages of the friction-drag, and other contrivances, are said to be, 1st. The method, which 

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



