260 



THE AMEKICAN MONTHLY [November, 



The Analyzing Eye-Piece. 



By WILLIAM LIGHTON, 



OMAHA, NEBB. 



At the first meeting of the American Society of Microscopists, 

 held at Indianapolis, I presented a paper upon an Analyzing 

 Eye-Piece, and exhibited one that I had been using for several 

 years. I sent, at a later date, a drawing and description of it to 

 the San Francisco Microscopical vSociety. I have had many let- 

 ters from microscopists since that time asking about the appli- 

 ance, and I have been strongly urged lately to present the matter 

 through the Af?ierican Monthly Alicroscopical Journal. 



The apparatus consists of a box, A^ of the form shown in the 

 side view, fig. i, made of either metal or wood, and contain- 

 ing a plate of polished black glass, B. At the lower part of this 

 box is a short tube, C, which fits into the draw-tube of the micro- 

 scope, and at the opposite angle of the box is another short tube, 

 /?, which receives the eye-piece. The glass- plate is used for the 

 purpose of reflecting the beams of polarized light at the best an- 

 alyzing angle. It will be necessary, of course, to use some form 

 of polarizer below the object upon the stage of the microscope, 

 and the best is the Nicols prism. 



Lighton's Analyzing Eye-piece. 



The line E represents a ray of light which has been reflected by 

 the concave mirror through the Nicols prism and objective, and 

 is reflected by the polished surface of the glass B through the axis 

 of the eye-piece, as shown by the line F. G represents the eye- 

 piece. 



The exact angle of inclination of the polished surface of the 



