70 THE CHANGES IN THE GALLOP. 



' momentum ' (as well as to the extension), so far as 

 the order In which the feet leave the ground is con- 

 cerned. For instance, in illustration of the latter 

 proposition, in the slow gallops a hind-leg must 

 remain long enough upon the ground to drive the 

 mass over the planted leading fore-leg (and so we 

 get one of the positions In which three legs have 

 touched the ground at the same time), whereas In 

 the extended gallops the momentum Is so great 

 that this continued impulse from the hind-quarters 

 Is not required, and the horse is so extended that it 

 could not be given. 



T'RINTED liY T. AND A. CONSTABLE, PRINTERS TO HER MAJESTY, 

 AT THE EDINBURGH UNIVERSITY PRESS, 



