4 Michelson and Stratton — New Harmonic Analyzer. 



The resultant motion is recorded by a pen connected with u 

 by a fine wire w. Under the pen a slide moves with a speed 

 proportional to the angular motion of the cone D. (Plate I.) 

 To represent the succession of terms of a Fourier series the 

 excentrics have periods increasing in regular succession from 

 one to eighty. This is accomplished by gearing to each excen- 

 tric a wheel, the number of whose teeth is in the proper ratio. 

 These last are all fastened together on the same axis and form 

 the cone D. (Plate I.) 



^F 



A, one term ; B, five terms ; C, 

 terms; 



nine terms; D, thirteen terms: 

 F, seventy-nine terms. 



E, twenty one 



Turning the cone will produce at the points (x) motions cor- 

 responding to cos0, cos 20, cos 30, etc., up to cos 800, and whose 

 amplitudes depend on the distances d. The motion of the ele- 

 ments may also be changed from sine to cosine by disengaging 

 the cone and turning all of the excentrics through 90° by 

 means of a long pinion which can be thrown in gear with all 

 of the excentric wheels at once. 



The efficiency- and accuracy of the machine is well illustrated 

 in the summation of Fourier series shown in the accompany- 

 ing figures. 



Figure 2 shows the dependence of the accuracy of a particu- 

 lar function on the number of terms of the series. Figures 3, 

 4, 5, 6 and 7 are illustrations of a number of standard forms, 

 and 8, 9 and 10 illustrate the use of the machine in construct- 

 ing curves representing functions which scarcely admit of 

 other analytical expression. 



The machine is capable not only of summing up any given 

 trigonometrical series but can also perform the inverse process 



