THE INDUCTION MOTOR. 



Opening the slots has a decided tendency to diminish the load loss 

 considerably, therefore it is probable that the seat of this waste of 

 energy is in the bridges. 



38. It has often been advocated to calculate the leakage fields from the 

 dimensions of the slots, of the air-gap, of the pole-pitch, and so forth, 

 and it has been claimed that great accuracy is thus obtainable. I am 

 not of that opinion. Though I am perfectly aware that it is possible 

 at least theoretically to calculate the leakage, yet I cannot close 

 my eyes to the fact that such calculations are, of necessity, based upon 

 a good deal of guesswork ; the designer who chooses this pa.th is like 

 a man groping in the dark with here and there a guiding light, or, as 

 I should rather say, a will-o'-the-wisp, sometimes guiding him aright, 

 but much oftener leading him astray. I am suspicious of the a priori 

 method ; it has proved utterly vicious in all departments of human 

 knowledge. Upon a sound experimental foundation any mathematical 

 superstructure may be safely reared ; and no desire to obtain a knowl- 

 edge of things, which are in their very nature not yet clearly under- 

 stood, should mislead us to build upon the quicksand of imagined data. 



The succeeding chapter will be devoted to an exposition of the fac- 

 tors which enter into the equation for the leakage coefficient. 



