the Elasticity of Wires. 417 



would be of interest to extend these experiments to wires of 

 larger diameter; this suggestion was followed with results 

 appended below. 



In the author's experiments six different wires were used 

 (one of which was hollow), of diameters varying from ^inch 

 to 1 inch. These diameters are greater than those measured 

 by Mr. Searle (which were from J5 inch to -^ inch) ; thus 

 necessitating a much larger apparatus— the moment of inertia 

 of the vibrating rods being over six times as great. 



It is not necessary to repeat the mathematical theory given 

 by Mr. Searle, but the apparatus is shown in fig. 1. 



Fio-. 1. 



/A 



£ 



Jr 



Um 



NP and LM are square bars with holes drilled at R and S 

 to admit the wire under test at RS. H and K are two 

 j^-inch screws by means of which the vibrating wire is 

 clamped and the apparatus supported. 



The method of experiment is as follows: — The apparatus is 

 suspended so that the two swinging bars are in a horizontal 

 plane ; the ends at M and P are next inclined to each other 

 and tied with strong cotton-thread. When the apparatus has 

 come to rest, this thread is burnt and the number of swings 

 per second is estimated by timing a convenient number with 

 a stop-watch. The period so obtained is called t x . 



It is an important experimental point that, owing to non- 

 uniformity of diameter in the wire under test, the two rods 

 should be rotated relative to the wire through 90°, and a 

 re-determination of t l made. In the following experiments 



