EESEARCHES IN SOUND. 

 The following table gives the results : 



479 



From these experiments it would appear that the material or elasti- 

 city of the trumpet had little or no effect on the penetrating power of 

 the sound, although the shape appeared to have some effect, the pyri- 

 midal trumpet, or one with square cross-section (No. 1), giving a less re- 

 sult than the conical ones of the same sectional area. A comparison 

 was made between a long straight trumpet and one of the same length 

 curved at its upper end, which gave the same penetrating power with 

 the same pressure. It is probable that a thin metallic trumpet would 

 give greater lateral divergency to the sound, and also a slightly differ- 

 ent tone. 



8. The effect of a hopper-formed reflector was next tried with the 

 whistle, the axis of which was about 5 feet in length, the mouth C feet 

 square, and the small end about 18 inches. When the whistle was 

 sounded at the small end of this reflector, the distance at which the 

 sand ceased to move was 51 ; the sound of the same whistle without the 

 reflector ceased to move the sand at 40. The ratio of these distances 

 would have been less with a more sensitive instrument at a greater dis- 

 tance on account of the div^ergeucy of the rays. 



9. In order to determine the diminution of sound by departing from 

 the axis of the trumpet, a series of experiments was made with a ro- 

 tating trumpet, the axis of which was at first directed along the gradu- 

 ated liue of observation, and subsequently deflected from that line a 

 given number of degrees. The following were the results : 



These results illustrate very strikingly the tendency of sound to spread 

 on either side of the axis of the trumpet; had the experiments been made 

 with a more sensitive instrument, and at a greater distance, the effect 



