54 Journal of the Asiatic Society of Bengal. [February, 1914 



5 

 5 



-<3 



--4 



it 4 



S f M ■* 16 



£ iongdtion in A. 1 * cm. 



e 



zo 



determining 



88*5 cms. 



-031 cm. 

 140. 



Fig. II. 



Example of an Experiment. 



The following are the observations made in 

 the load-elongation curve of copper : 



Length of copper wire No. 30 B.W.G. 



Diameter of the wire 



Magnification of the apparatus as arranged . . 



Elongation x 140 in cms. 



20 



2-8 



3-6 



4-4 



5-8 



7*8— (elastic limit exceeded) 



9-8 

 105 

 115 

 131 

 149 

 18-2— (secular change begins) 



The curve Fig. II shows the load-elongation curve for the 

 specimen of copper wire, as obtained from the above obser- 

 vations. From the straight portion of the curve it is found 

 that when the load is 200 grams the elongation is 3*3/140 cm., 

 whence the value of Young's modulus is found to be equal to 

 94 x 10 ' * dynes cm. 2 The value obtained for the same speci- 

 men by the ordinary laboratory method (scale and vernier) was 

 .89 x 10 !i dynes cm. 1 



Load in grams. 



118 

 168 



218 

 •J 68 

 352 

 452 

 502 

 522 

 542 

 592 

 644 

 700 



