ii-A] WAVE ANALYSIS. 335 



For the origin of the method, see Appendix I. ; for the determina- 

 tion of even as well as odd harmonics, see Appendix II. 



6. Procedure. Ascertain the values of 18 equidistant ordi- 

 nates distributed over any interval of 180, as y^y^y 2 ^17 i n 

 Fig. 2, the ordinates being determined for every 10 degrees. The 

 initial ordinate ;y may have any position whatsoever, without 

 reference to the zero or maximum of the curve; y 18 >yi9> etc., are 

 repetitions of y ,y lf etc., and are not used, unless y and y ls , y 

 and 3' 19 , etc., are averaged for greater accuracy. In all cases care 

 should be taken to note the algebraic sign ; all additions, subtrac- 

 tions and multiplications are algebraic. 



7. Scheme. Arrange the 18 ordinates in a scheme as shown. 



SCHEME (18 ordinates). 



y<> yi y a y s y* y* y :v 7 y & y*' 

 yii yie y y ? y y^ y 



Sums s t s 2 s 3 s 4 s 5 S Q s 7 s 8 s 9 



Differences d d^ d 2 d 3 d 4 d 5 d Q d r d s 



Write the algebraic sums and differences as indicated, where 



Certain of the values thus obtained are further combined, alge- 

 braically, in the following manner : 



