HOW TO BIDE. 17 



soft ground, then put a weight precisely in the centre of the table, and 

 measure the depth to which the feet have been forced into the soil; you will 

 find it to be the same for all four feet, if the surface on which the table 

 stands be equally soft througliout ; then shift the table a few inches, having 

 previously removed the weight, and place this near one of the ends, instead 

 of in the middle ; measure again, and you will find that the pair of legs 

 nearest to the weight have penetrated much deeper than the others ; there- 

 fore, on a horse, in order to equalize the pressure, the rider's weight should 

 be placed in the centre of the saddle. 



But this is not all. Place a piece of stout board about two feet long on 

 the ground, stand on one end of it, and you will find that the other loses its 

 contact with the ground, and is more or less tilted up into the air ; the 

 board has become a lever. Now, make a motion as if about to jump, but 

 without quitting your position on the board ; this latter will, being out of 

 contact with the ground at the further end, be shoved onwards in that 

 direction. This is precisely what happens when a rider sits at one end of 

 the saddle, generally the hinder one ; this one is pressed down into the 

 horse's back, the other, the front end, is tilted up, and at every movement 

 of the horse and rider the whole saddle is shoved forward till stopped by 

 the withers, which it will probably wound. 



We may now go a step farther. Suppose the saddle be placed with its 

 centre exactly over the combined centres of gravity and motion, and the 

 rider in the centre of the saddle, there will be, first, an equable distribution 

 of the combined weight of horse and rider on all four legs, both in a state 

 of rest and action ; secondly, the movements of the horse, centring in this 

 point, have the least possible tendency to disturb the seat of the rider or 

 the position of the saddle ; thirdly, the weight of the rider, being equally 

 distributed over the whole surface of the saddle in contact with the horse's 

 back, is therefore less likely to injure any one portion of this ; nor does it 

 convert the saddle into a lever, and shove it forwards or backwards. 



Again, let us suppose the saddle as before, but the rider sitting altogether 

 at its hinder end, for instance, and there will be, first, the horse's equilibrium 

 destroyed ; secondly, the rider himself, being nearer to the hind legs, will 

 first receive an impulse from that direction, and be thrown forward till he 

 meets that coming from the opposite direction ; and these two forces, instead 

 of resolving each other from one common point into their sum total, neu- 



