378 HIGHWAYS AND HORSES. 



as the bearing of the collar is concerned, a horse 

 can draw from a low splinter-bar with far greater 

 comfort than from a high one.'" 



The strong iron which extends across and beneath 

 the wood-work of the under-carriage, is, as every one 

 knows, called the axle-tree ; the round parts at each 

 end, on which the wheel runs, are called the axle- 

 arms ; the nave of the wheel is pierced through the 

 centre with a large hole to introduce the box or 

 iron tube, for the axle-arm. It has frequently been 

 proposed to make metal naves, or centre pieces for 

 wheels ; the objection to this was that if the wood 

 of the spokes were to shrink, they would become 

 loose in the mortises, whereas a wooden nave would 

 shrink at the same time with the spoke. 



The word axle-tree was evidently derived from 

 the fact that axles used to be made of wood, the 

 stem of a tree being frequently employed for the 

 purpose. The axle-tree and box most in use for 

 light carriages is " Collinge's Patent Cylindrical Axle- 

 tree and Box." These axle-trees have been a con- 

 siderable time in use, and their advantages have 

 been proved in the length of time they wear, in the 

 silent and steady motion they preserve to the wheels, 

 in the advantage of retaining the oil to prosecute 

 a journey of two thousand miles without being 

 once replenished ; and lastly, they are very 

 durable and but little subject to be out of order. 

 The axle-tree arm is made as perfectly cylindrical 

 as possible and of a peculiar hard substance ; the 

 middle of the cylinder is reduced, to contain 

 the oil necessary to feed the axle-trees, so that 



* But to meet these objections a middle course should be adopted, 

 and regard should be had to the shape of the horse's shoulder. The 

 collar should rest on the scapula or shoulder-blade, and should there 

 have a firm bearing. 



