On the true Wave-length of a Cylindrical Resonant Tube. 339 



or, the sectional area of an iron rod should be to the sectional 

 area of a copper rod in the ratio of 8 to 3. 



This result is an argument in favour of the use of iron as 

 being the less expensive. 



Calcutta, March 3, 1879. 



LIII. Experiments for determining the Correction to be added 

 to the Length of a Cylindrical Resonant Tube to find the true 

 Wave-length, and the Velocity of Sound in small Tubes. 



To the Editors of the Philosophical Magazine and Journal, 

 Gentlemen, 



I BEG to submit to your consideration for publication the 

 accompanying memorandum of experiments made by me 

 with the object of determining the correction to be added to 

 the length of a cylindrical resonant tube to find the true 

 wave-length, and the velocity of sound in small tubes. 



They give results, as regards the first point, in the main 

 confirmatory of those already arrived at by Lord Eayleigh 

 and Mr. R. H. M. Bosanquet; but the methods of experi- 

 ment followed by me being different to theirs, the notes may 

 be of interest. As regards the second point I am not aware 

 of any experimental results having been published. 



I am, Gentlemen, 

 5 Compton Place, Yours obediently, 

 Canonburj N jy j. BlAIKLEV. 



March 22, 18/9. 



The first method of experiment adopted by me is applica- 

 ble only to tubes closed at one end, and consists in determin- 

 ing in a tube of indefinite length the positions of the first and 

 second nodes of a wave excited by a fork held over its mouth, 

 the tube having one end sunk in water, and the water-level 

 at the position giving maximum resonance determining the 

 position of the node. The tube used was made of thin brass, 

 and had an internal diameter of 2'08 inches ; it was slung 

 with a pulley and counterweight over a deep vessel of water, 

 and its height out of the water at each observation read off by 

 a scale. The advantage of the use of water instead of a sliding 

 solid plug is that there is not the slightest noise to interfere 

 with the appreciation of the point of maximum resonance. 



The forks used were d 253'55 vibrations, e' 317-3, g r 

 380-625, P 444-5, and c" 507-2 Of these I had an oppor- 

 tunity of comparing all but the e' with Scheibler's standards 

 in August last, through the kindness of Mr. A. J. Ellis. 



The pitch of Scheibler's forks being determined at about 

 70° F., and the variation being about '00005 per vibration 



