218 



ANNUAL EEPORT SMITHSONIAN INSTITUTION, 1908. 



Fig. 9. — Tapering sound arm (a). 



move across the turntable and also to be raised or lowered above the 

 record. This arrangement offered the advantage that the weight of 



the horn was carried by the 

 cabinet, and the record had not 

 to overcome the inertia of the 

 whole horn as before, but only 

 had to move the sound box 

 and its connecting tubing (or 

 sound arm as it is called) when 

 the turntable was not hori- 

 zontal or the hole in the record 

 not central. But though this 

 arrangement offered advan- 

 tages in one direction, it was 

 found to be accompanied by imperfection in another. The piece of 

 straight tubing connecting the sound box and the horn had a dis- 

 torting effect upon the 

 sound waves. Instead 

 of these waves being- 

 able to expand uni- 

 formly as they ad- 

 vanced, as had been the 

 case in the old arrange- 

 ment when they passed 

 straight into the horn, 

 they were forced to 

 pass first of all through 

 this straight pipe where 

 the waves became dis- 

 torted and acoustic in- 

 terference was created. 

 It was not until 1903 

 that patents were taken 

 out on an invention 

 which overcame this 

 difficulty (fig. 9), the 

 invention now known 

 as the taper arm, the 

 patent on which in this 

 country w^as recently 

 upheld in the court of 

 appeal. The inventor 

 had hit upon the idea 

 of jointing the amplif}^- 

 ing horn itself, so that while the horn could start immediately next 

 the sound box the latter could be moved Avith freedom without mov- 



FiG. 10a. 



Some various stages of development of tbe 

 gramophone. 



