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BELL SYSTEM TECHNICAL JOURNAL 



Bei.l System Photomicrographic Laboratory 



A general view of the Laboratory situated on the fifth floor of the 

 building at 463 West Street, New York City, is shown in Fig. 15. 

 Some of the equipment is more fully illustrated in detail views. 



It consists of two metallurgical equipments, one of which is the 

 large Zeiss metallographic outfit shown in the foreground of Fig. 15. 

 This equipment is of precision quality and is used for all classes of 



Fig. 16 — The Martens stand of the large metallographic outfit. The vertical illum- 

 inator is shown between the barrel of the microscope and the objective. 



work involving opaque specimens. The optical parts consist of a 

 full complement of Zci.ss apochromatic objectives and compensating 

 eyepieces for medium and high-power work. For low-power work 

 a full set of Zeiss micro-planar lenses and a Tessar lens are used. 

 The maximum bellows extension of the camera is 155 centimeters 

 and the plate holders are designed for 24 x 30 centimeter plates and 

 all smaller sizes by employing suitable kits. The illuminating train 

 consists of an automatic arc lamp, a condensing system, and cooling 

 cells, mounted on an optical bench and capable of adjustment to 

 meet the conditions of the work. 



Illuminators of conventional t>pes, for vertical and oblique light 

 may be assembled on the Martens t>"pe stand. This stand is a 

 departure from the construction of the usual form of microscope 

 stand. It is much more rugged and is arranged for use in a horizontal 



