﻿Plale 
  LVI. 
  

  

  THE 
  GRADIENTEK. 
  

  

  Instniment- 
  for 
  Topoj^aphical 
  purposes 
  

  

  AM. 
  PHOTO-LITHO. 
  CO. 
  N.Y. 
  lOSBORNE'S 
  PROCESSj 
  

  

  