QUAKTX FIl'.Us AND ITS I I \! I KKATURE COEFFICIENT. 



Ill 



tlir observations for the absolute value of the modulus it had already been observed 

 tli.it the period of torsional vibration diminished slightly as time went on, thus 

 indicating an increase iii the rigidity of the fibre. This was also shown in some of 

 the observations at higher temperatures, but the effect was not nearly so marked as 

 in tin- C.-IM- of metal \\ires. In fact, in some instances the rigidity apparently 

 diminished slightly <>n keeping the fibre for some time at a high temperature. 



In addition (,, tin- determination of the periods of vibration, observations of the 

 logarithmic decrements nf tin- amplitudes nf the nscillatinns were taken at each 

 temperature, in order in obtain the correction to apply to the periods for the damping 

 of (he torsional oseillat ions. 



Mi example of the "1 '-> T\ a t ions taken I gi\e In-low the figures obtained with 

 the tirst fibre experimented on over this range of temperature. The periods in tin- 

 table are each the mean of manv observations. They ha\e been corrected for clock 

 rate, t'or the expansion of the fibre and vibrator, and also for the damping of the 

 vibrations. 



From the numbeis -iven in the table it will !* seen that, after the first heating of 

 the fibre, the rigidity at the lo\\er temperature d<H-.s not come back to its original 



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