and Laboratory Methods. 1925 



one side, in front of whicli is arranged a system of condensing lenses (B), sim- 

 ilar to those used in high-grade projection lanterns ; a cell filled with a saturated 

 solution of alum (C), to absorb the heat rays ; a double-convex lens (D), to fur- 

 ther concentrate the beam of light ; a holder for color and ground-glass screens 

 (E) ; an iris diaphragm and a photographic shutter (F) with pneumatic release ; 

 and probably another double convex lens (G), all of which are so secured to the 

 optical bench as to be movable in a horizontal direction for the purpose of focus- 

 ing the light on the vertical illuminator. All the members of this system are 

 also adjustible vertically, so they may be brought into alignment with the source 

 of light. 



The beam of light leaving the lens system enters the body of the microscope 

 (H, whose tube is vertical), through the opening of the vertical illuminator, 

 inserted between the objective and the main tube. The vertical illuminator con- 



J K M 



Fig. S. — Optical Bench for Photo-microscopy of Metals. 



tains either a plain glass disk reflector or a total reflection prism, which changes 

 the direction of the horizontal beam of light to a perpendicularly descending 

 beam. The objective of the microscope acts still further as a condenser and an 

 exceedingly well-illuminated spot is thus secured on an opaque body. 



The camera used in the photomicrography of metals is generally one adapted 

 to 4x5 inch plates, and is so arranged that it may be swung out of the observer's 

 way while an examination is made. The cut shows it in this position. When 

 the part to be photographed is selected the eye-piece of the microscope is removed, 

 the collar (K) to connect the microscope and the camera is placed over the end 

 of the tube and the eye-piece is replaced within the collar. The camera is 

 swung into position vertically over the microscope, the front board of the camera 

 is lowered until its collar telescopes with that on the microscope. The upper, 

 or ground glass, end of the camera is moved up or down until the circle of the 

 projected image is the size desired. The ground glass of the camera has 

 cemented to its center a large cover-glass, giving a clear-glass spot in the middle 

 of the image. The fi»al focusing for sharpness and clearness of the micro- 



