THE THEORY OF DIABOLO 571 



which is so inexpensive, simple, and handy as the now popular 

 diabolo. It is whispered that mathematical professors do 

 not always illustrate what they wish very successfully when 

 using gyrostats and Maxwell and other tops. The diabolo 

 seems to have been invented for their special benefit. A 

 complete and proper demonstration of the points described 

 above, and of many others, no doubt, would add enormously 

 to the joy of the class. If at any time the spool should prove 

 refractory the expositor could fall back upon the convenient 

 formula tan 6 = ^2, which in time might be contracted to tan, 

 and would so serve the double purpose of an explanation and 

 a harmless but comforting expletive. As a game I do not 

 at all feel inclined to agree with the view that it is not worth 

 while, that it is silly, that it is a mere passing craze. It may, 

 and no doubt will, go out of fashion as quickly as it came in, 

 if indeed it has not already done so, but that is not the fault of 

 the game but of society, who equally threw over cycling before 

 the motor car had destroyed that invigorating pursuit. 



