﻿556 
  

  

  Williams— 
  Twist 
  in 
  Steel 
  and 
  Nickel 
  Rods. 
  

  

  Fig. 
  1. 
  

  

  Film 
  T 
  2 
  

  

  Film 
  Ti 
  

  

  Fig. 
  1 
  Nickel 
  Rod, 
  No. 
  5. 
  

  

  