HOW TO RIDE. 15 



is in action. For there is one bone in each of the hind and fore legs 

 through which the remainder of the limb acts as a lever on the whole frame, 

 either for the purpose of propelling it (hind legs), or supporting and lifting 

 it (fore legs). These are the thigh-bone and the arm-bone, whose upper 

 ends have their fulcrums or points of support in the hip-bones and shoulder- 

 blades. 



It is therefore evident that, both in a state of rest and of action, the 

 fourteenth vertebra is constantly the centre of motion. 



THE INFLUENCE OF THE SADDLE ON THE SEAT. 



It would be only reasonable, one would suppose, to accommodate our 

 saddles to our seats, just as we do every other instrument to the purposes 

 for which it is intended ; but this is precisely what is very seldom done, 

 and in the great majority of instances the rider sits his horse just in the 

 fashion his saddle allows, or, perhaps, compels him to do. It is therefore 

 a matter of some importance to understand clearly the mechanical princi- 

 ples applicable to this piece of horse-furniture, as it will enable every rider 

 to ascertain exactly what he wants, and how to attain his object, whatever 

 that may be, as also to save his horse's back. 



To begin with the under surface of the saddle — the portion coming in 

 contact with the horse's back — we find two principal points for considera- 

 tion, — its shape or form, and its size or extent. One general mechanical 

 principle applies to both, namely, that the larger the surface over which 

 a given amount of pressure is equably spread or divided, the less will be 

 the action on any given point of the other surface in contact ; and this 

 translated into plain English means, as regards shape, that the under sur- 

 face of the saddle should bear as nearly as possible the same relation to 

 that part of the horse's back it is intended to occupy, as a mould does to 

 the cast that is taken from it, always saving and excepting that strip lying 



