( 227 ) 



the motion of the string was again caused by friction of the air 

 only. Hence we may identify r with Va- The results of the calculation 

 are found assembled in the following table IV. 



TABLE IV. 



Also these results lack the accuracy which can be obtained when 

 the motion of the string is slow. The difficulty lies in the value of 

 h which, as Av^as remarked before, presents a great uncertainty. 



In the following table V the axerage values Va are given as they 



TABLE V. 



Number 

 of the 

 quartz 

 thread. 



Ta 



with feeble 



tension of the 



quartz 



thread. 



ra 



with strong 

 tension of the 

 quartz thread. 



Ratio of ra with 

 strong tension 



to Ta 



with feeble tension. 



10 

 13 

 14 



0.0193 

 0.0174 

 0.0157 



(0.0201) 

 (0.0210) 

 (0.0199) 



1.04 

 1.21 

 1.27 



were found by calculation according to the tliree methods mentioned. 



We see that the value of Va is a little greater with a greater 

 tension of the quartz thread. From this we must infer that the 

 resistance, caused by the friction of the air, does not increase quite 

 proportionally to the velocity of motion of the string, but that with 

 very rapid motions of the string the mcrease of the resistance of the 

 air is a little greater. 



Practically, however, this result has no influence on our further 

 calculations. The increase in the x'aliie of Va may be called very 

 small. The greatest increase was in the ratio of 1 : 1,27, while 



16* 



