PREFACE V 



The point at which the book ought to close seemed in the pres- 

 ent instance to be determined by the method of the book itself. 

 If, as I believe, a study of physical principles ought to be the com- 

 mon preliminary to the study of every branch and every appli- 

 cation of mechanical science, then the book might clearly try to 

 cover all this common ground, and ought to stop at the point at 

 which detailed specialization becomes feasible and profitable. It 

 ought, in fact, to cover the range which will be covered by all stu- 

 dents, and stop short of subjects which will be of interest or impor- 

 tance only to a few. Judged by this criterion the book will perhaps 

 be thought by some to be open to the criticism of covering too much 

 ground; it may be thought that the final chapter on generalized 

 coordinates can hardly be regarded as essential to the student 

 whose study of mechanics is a preliminary to his entering the pro- 

 fession of, say, engineering. I am nevertheless convinced that, even 

 if the study of generalized coordinates is not absolutely indispen- 

 sable to such students, it is of extreme value and ought not to be 

 neglected by a student, possessed of the requisite ability, who can 

 possibly find time for it. The student who omits it shuts himself 

 off from a point of view which sums up and illuminates the whole 

 of dynamical theory; at the same time he denies himself the 

 opportunity of studying, or at least of fully understanding, the 

 theory of electricity and magnetism. And as regards the student 

 who intends to continue his studies in the direction of theoretical 

 physics, the theory of generalized coordinates formS so essential 

 a preliminary to the study of most branches of physics that the 

 advantages of including a short treatment of this subject in the 

 preliminary mechanics course will hardly be disputed. 



PRINCETON J - H 



November, 1906 



