﻿DlJFFIELD. 
  

  

  Phil. 
  Mag. 
  Ser. 
  6, 
  Vol. 
  26, 
  PL 
  II. 
  

  

  Fig. 
  1. 
  

  

  SiUty 
  — 
  (Ycj4lw€ 
  Stiver 
  JPouhuc. 
  

  

  Fig. 
  3. 
  

  

  Fig. 
  4. 
  

  

  