486 



W. Mason — Neiv Harmonic Analyzer. 



fit into holes on the curve and hold it in place. A series 

 of transparent zylonite pieces, one for each sine or cosine 

 harmonic, on which particular curves have been engraved, 

 are the instrument curves referred to. An arm, made 

 partly of metal, and partly of a zylonite strip on which a 

 straight line has been engraved, is fastened to the frame- 

 work by means of a pivot 0. Fig. 1 illustrates this 

 construction. At the end of this arm a small hole P is 

 bored, in which either a pencil point or the tracing point of 

 a planimeter may be placed. A straight edge fastened 

 to the board on the axis of integration, which is always 



Fig. 2. 



the Y axis if the curve extends along the X axis, serves 

 as a guide for the machine. The essential operation con- 

 sists in tracing the wave form to be analyzed with the 

 intersection of the arm and the instrument curve, and at 

 the same time drawing the derived area by means of a 

 pencil point placed in the tracing point of the analyzer. 

 It can be seen from fig. 2, that any ordinate of the wave 

 form is exactly reproduced in the derived area, for when 

 X is constant, the arm is fixed, and draws one ordinate as 

 long as the other. Therefore, since {y/-y/) ^y in 

 equation (5), these factors can be cancelled out leaving 

 the equation 



