Transverse Vibrations of a Stretched Indiarubber Cord. 347 



by leakage. This was not of course in connexion with the use 

 of Price's ingenious guard-wire, but in the days of the old 

 " divided-ring electrometer," before it was known how to 

 make a quadrant electrometer with the deflexions directly 

 proportional to the P.D. to be observed, and when, therefore, 

 a zero method had to be employed in carving out the " loss 

 of charge " insulation test. 



XXXII. The Frequency of Transverse Vibrations of a 

 Stretched Indiarubber Cord. By T. J. Baker, B.Sc* 



THE writer has observed that the pitch of the note pro- 

 duced by twanging an indiarubber band which is 

 stretched over the fingers is influenced but little by the 

 tension, particularly if this is considerable. 



The matter appeared worthy of further investigation ; and 

 for this purpose a short piece of indiarubber cord, of square 

 section, was attached at one end to the middle of a tambourine- 

 diaphragm, while the other end was bound to a piece of twine 

 which passed over a pulley-wheel and supported a weighed 

 scale-pan . 



After placing a weight in the pan, the rubber was allowed 

 to stretch for some minutes, and then the end nearest the 

 pan was firmly clamped. The intensity of the note pro- 

 duced by transverse vibrations of the cord was rendered 

 sufficiently great by the tambourine to permit a determi- 

 nation of pitch by comparison with a sonometer and tuning- 

 fork. 



The sectional area of the cord under the various tensions 

 employed was determined by measurements of its two dia- 

 meters at three different points in its length. 



For this purpose a micrometer-gauge reading to *001 cm. 

 was employed. The observations were continued until the 

 cord broke. This happened when its length had increased 

 six-fold. The 38 sets of values thus obtained were plotted on 

 squared paper, and three curves were drawn showing the 

 relation between — 



(i.) Length and tension, 

 (ii.) Length and sectional area. 

 (iii.) Length and frequency. 



The smoothing-out of slight experimental irregularities 



* Communicated by the Physical Society : read Jan. 26th, 1900. 

 2B2 



