Bronson — Transverse Vibrations of Helical Springs. 69 







Table VIII. (Spring 7.) 









T + x 







T. 



L. 



L. 



L. 



n. 







8-43 





10 



9*32 



5 



8*69 





11 



9-18 



10 



9-37 





12 



9-01 



15 



10-63 





13 



8-86 



20 



12-31 





14 



8-84 



25 



14-22 



1-990 



15 



8-81 



30 



16-42 



2-028 



16 



8-79 



35 



18-80 



2-037 



18 



8-78 



40 



21 23 



2-040 



20 



8-77 



45 



23-66 



2-041 



22 



8-78 



50 



26-09 



2-043 



24 



8-77 



55 



28-51 



2-045 



26 



8-76 



60 



30-90 



2-048 



28 

 30 

 32 



8-78 

 8-76 

 8-76 



In calculating the ratio of T to L, a small correction x equal 

 to about one half the weight of the spring was added to T. As 

 was expected, the frequency was very constant through the same 



range that 



T+x 

 L 



was constant. 



Sufficient evidence, I think, has been furnished to show that 

 vibrating helical springs obey the same law as vibrating strings 

 through a considerable range of length and tension. It would 

 seem of interest now to examine the behavior of india-rubber 

 cords under conditions as similar as possible to those experienced 

 by the springs and to compare their behavior. For this pur- 



mw- 



pose two samples of as pure rubber as could be obtained were 

 used ; one a rubber tube of about 4*68 mm. external and 3*06 

 mm. internal diameter, the other a rubber cord of square cross 

 section, 1*16 mm. on a side. 



The observations were taken in the same way as in the case 

 of the springs, except that a slight modification had to be made 

 in order to get electrical connection. In the case of the rubber 

 tube a [)-shaped piece of wire was hung on its center and held 

 fast with rubber cement. The vibrations of the tube caused 

 the two ends of the wire to dip into two mercury cups. In the 



