The Decticus: his Instrument 



tions are imparted to it after starting else- 

 where. And how ? I will tell you. 



Its edging is prolonged at the inner angle 

 of the base by a wide, blunt tooth, furnished 

 at the end with a more prominent and power- 

 ful fold than the other nervures distributed 

 here and there. I will call this fold the 

 friction-nervure. This is the starting-point 

 of the concussion that makes the mirror re- 

 sound. The evidence will appear when the 

 remainder of the apparatus is known. 



This remainder, the motor mechanism, is 

 on the left wing-case, covering the other with 

 its flat edge. Outside, there is nothing re- 

 markable, unless it be and even then one 

 has to be on the look-out for it a sort of 

 slightly slanting, transversal pad, which 

 might very easily be taken for a thicker 

 nervure than the others. 



But examine the lower surface through the 

 magnifying-glass. The pad is much more 

 than an ordinary nervure. It is an instru- 

 ment of the highest precision, a magnificent 

 indented bow, marvellously regular on its 

 diminutive scale. Never did human industry, 

 when cutting metal for the most delicate 

 clockwork mechanism, achieve such perfec- 

 tion. Its shape is that of a curved spindle. 

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