71, 72] HAMILTON'S PRINCIPLE. 143 



Consequently a knowledge of the energy is not sufficient to 

 find the motion, while a knowledge of the Lagrangian function or 

 kinetic potential is. 



In case we wish to ignore some of the coordinates we may 

 modify the statement of Hamilton's Principle by the use of the 

 modified Lagrangian function and put 



where we suppose only those coordinates which are not ignored 

 are varied. 



