THREE-PHASE CURRENT MOTOR. 



most abstruse problems in natural philosophy. More and more we 

 begin to realize the truth of the words with which Kelvin and Tait 

 prefaced their lucid treatise on "Natural Philosophy," that "simpli- 

 fication of modes of proof is not merely an indication of advance in 

 our knowledge of a subject, but is also the surest guarantee of read- 

 iness for farther progress." 



92. Time was and that not very long ago when theories in which 

 mathematical methods were restricted to a minimum, were glibly 

 labeled "popular," with that fine flavor of contempt that hangs about 

 this term. Slowly but surely graphical methods have supplanted, 

 and will supplant in the future, highly analytical methods, 7 as in the 

 graphical method the development of the idea can be followed stage 

 by stage, thus furnishing a means of constantly checking the process 

 01 reasoning and keeping the attention of the mind concentrated 

 upon the development of the thought. While a long analytical argu- 

 ment, after starting out from certain premises, leaves us in large 

 measure in the dark until the result is reached. In my opinion the 

 didactic value of graphic methods is vested in the difference traced 

 out in the above comparison. 



93. These remarks must not be misconstrued. In many cases the 

 graphical treatment turns out to be far more complicated and weari- 

 some than the analytical treatment, and I need hardly say that in 

 such cases the latter is preferable. Whichever method is the simpler, 

 IM the case under consideration, deserves preference. 



'One of the most complex problems in natural philosophy is the theory of the 

 tides, on which the greatest mathematicians from the time of Newton until to- 

 day have tried their powers. This is what one of the workers in this field, Prof. 



analytically and numerically its bearings un the history of the earth. 



"Sir William Thomson, having read the paper, told me that he thought much 

 light might be thrown on the general physical meaning of the equation, by a 

 comparison of the equation of conservation of moment of momentum with the 

 energy of the system for various configurations, and he suggested the appropri- 

 ateness of geometrical illustration for the purpose of this comparison. 



"The simplicity with which complicated mechanical interactions may be thus 

 traced out geometrically to their results appears truly remarkable." 



S3 



