The Framework of the IIo 



49 



in sailing a boat out of trim ends in a capsize, or in 

 carrying away spars at least ; just as riding out of trim 

 usually terminates in a "purl," and always in the prem- 

 ature destruction of the horse's legs. 



And just as too heavy a bowsprit or jib-boom will 

 destroy the trim of a boat, the overhanging position of 

 the horse's head and neck destroys the animal's proper 

 trim after a rider is placed on its back ; and the ques- 

 tion is, therefore, how this may be remedied, seeing that 

 we cannot shift a head and neck like a jib-boom. Fig. 

 3 shows three levers, d N^d O^ d P^ of equal length, 



Fig. 3- 



all moving round the same common centre or prop d, 

 which corresponds to the junction of the vertebrae of the 

 neck with those of the back in the horse. Now the 

 longer the lever the greater its power — that is to say, a 

 given weight will act more powerfully at the extremity 

 of a long lever than of a short one, in the exact propor- 

 tion of their relative lengths. The true expression is, 

 however, that a given weight acting on a lever of this 

 kind exercises a downward (perpendicular) pressure in 

 direct proportion to the distance at which the perpen- 

 dicular from (or through) it falls from the prop. There- 

 fore, if the head and neck, d i\^, be stretched out hori- 

 zontally, the relative weight is rejDresented by the whole 

 5 D 



