60 Bronson — Transverse Vibrations of Helical Springs. 



Observatory clock showed that the rate of the clock used was 

 entirely negligible for the purpose in hand. 



Figures 1, 2 and 3 show the arrangement of the apparatus 

 for holding the spring and starting the vibrations. JOT, fig. 1, 

 is the base about 40 inches long and 1J inches thick. On the 



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back of this is a metre scale, from which the lengths of the 

 spring were read directly. One end of the spring was clamped 

 to the fixed block B, the other to the movable block A. 



It was found quite difficult to clamp the ends of the springs 

 in any manner which did not have an appreciable effect on the 

 frequency. The method finally adopted is shown in fig. 2. The 

 last turn of the spring was drawn close up to the block by means 

 of two fine wires fastened at c and d, which are the extremities 

 of its horizontal diameter. These two wires were then clamped 

 between the blocks E and F, and held the spring very firmly, 

 yet with very little constraint. 



A fine wire fastened to the center of the spring made con- 

 tact with a mercury cup at each vibration. The chronograph 

 was adjusted delicately enough to record signals with frequency 

 as high as thirty-five per second. 



In order to have uniformity in the amplitude of the vibra- 

 tions, it was found convenient to use an apparatus of which 

 fig. 3 is a diagrammatical sketch, a b is a wooden arm about 9 

 inches long pivoted at a; d is a stop which can be adjusted so 

 that the end b will start the spring vibrating with the desired 

 amplitude; the spring c is strong enough to release the spring 

 without interfering with its vibration. 



Observations and Calculations. 



The method of making the observations in the case of springs 



1, 2 and 6 was as follows : — The relation between the length 



and tension was determined, the tension being first increased 



from zero until the increase in length was no longer propor- 



