14 ART. 10. S. KUSAKABE. 



These two values for the frequency in free vibration are equal to 

 €ach other within the error of observation. 



In the above observations, the tension of the string remained 

 constant and equal to 



TF= 30-718 grams. 



To test whether the error of observation is affected by the varia- 

 tion of the constant tension or not, two other observations were 

 made on the same specimen, giving the result ; 



TF=30-718, n = i09'7 



TF=20-908, 71=411-4 



F=ll-065, n =409-1 



Now, taking the mean of the above values, the data required 

 to calculate the modulus of elasticity of the sandstone are 



L=9-9 

 ^>=1-16 

 P =2-25 

 n =410-1 

 whence -ÈV=10-86x 10^'^ c.g.s. unit. 



It may be here noted that tlie value determined by the 

 static method is nearly half of the above, i.e. 



^s =5-7 X 10'*^ c.g.s. unit. 

 So far as the principle is concerned, the present method is 

 very simple, and it may be easily understood at a glance. The 

 mode of observation and the process of calculation, however, are 

 so tedious and complicated that the author considers it in no 

 case superfluous to recapitulate them. 



With a known tension ]F= TFi and a linear density tv = iVi 

 of the string and a certain frequency of the hammer m = nii, we 

 proceed as follows : — 



