﻿On the Plastic Bending of Metals. 



185 



incapable of exact mathematical treatment, and even an 

 approximate theory presents almost insuperable difficulties*. 



The present writer has obtained some empirical results for 

 Case b, which, in the absence of other information, seem to 

 him o£ sufficient interest to justify their publication. 



The measurements here recorded were made on thin wires 

 of commercially pure lead, but similar results have been 

 obtained with thin wires of tin and cadmium. The lead 

 wires were specially drawn for the experiment and were 

 kept straight and not wound on bobbins. They were laid aside 

 for several months at ordinary temperatures for annealing 

 purposes. 



Observations were made as follows : — 



A suitable length of wire, having one end fixed in a 

 horizontal clamp, was gently released by hand from the 

 horizontal position at a known instant. A number of whole- 

 plate photographs of the specimen, a vertical plumb-line, 

 and the recording timepiece, were taken at limes extending 

 in some cases over several days. The photographs were 

 taken against a black background, and accurate measure- 

 ments of the coordinates of any point on the specimen were 



Fk-. 2. 



Ofr- INITIAL POS/TION 



o b = Position 0-9 minutes after release 



0C= - 25-6 



0D= •< /53 



E = « 4430 ■■ 



obtained by laying the developed plate on squared paper and 



inspecting with a low-power microscope. Fig. 2 shows the 



* Vide Math, .and Physical Papers of Sir G. Stokes, vol. ii. p. ITS. 



