738 



Mr. J. It. Airey on the 



To realize the conditions of the problem practically, a 

 number of "blinds" were constructed, each consisting of 

 about fifty or sixty wood rods, with square cross-section, sides 

 one cm. long and fixed '25 cm. from one another. The 

 uppermost rod was generally about 40 cms. long. The 

 shape of the " blind " was determined by the curves y= ±cx n , 

 where n had the values £, §, f , 1, &c, the first curve being 

 a parabola, the fourth a triangle, &c. The rods were held in 

 position by means of a string passing tightly into vertical 



a 

 saw cuts at their ends. The whole arrangement was then 

 suspended from two loops on the string above the uppermost 

 od. 



The following observations were made of the times of 

 viDration in the different modes, ten sets of 100 vibrations 

 each being recorded for each mode. For comparison, the 

 values calculated from equation (1) have been added. The 

 roots of the equation J n (V) = are easily found from the 

 formula given by Prof McMahon. 



Mode of 



Value 



Length of 



Time of vibration 



Time of vibration 



vibration. 



Of 71. 



*' blind " 

 in cms. 



sees. 

 Calculated. 



sees. 

 Observed. 



1 



1 



107-1 



1-618 



1-629 



2 



2 





•809 



•817 



3 







•539 



•539 



4 







•404 



•402 



1 



2 



101-6 



1-547 



1-552 



2 



5 





•799 



•798 



3 







•539 



•536 



4 







•407 



•404 



1 



3 



87'9 



1-425 



1-437 



2 



4 





•747 



•745 



3 







•507 



•504 



4 







•384 



•375 



1 



1 



107-4 



1-535 



1-538 



2 







•838 



•835 



3 







•578 



•571 



4 







•441 



•437 



5 







•357 



•359 



1 



5 



86-4 



1-342 



1-352 



2 



4 





•758 



•758 



3 







•530 



•524 



4 



i 





•406 



•404 



