644 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



surface of the nicol produces a hazy appearance of the image. Fig. 81 

 represents a light-tight modification of the upper nicol of the FuessIIlA 

 Microscope. A vertical section through the carriage is shown at A. 

 A rotating collar a a' is moved by the lever c, and is supported by the 

 flanges b b' of the outer tube in which it rotates. A part of the scale d 



Q)^ 



D 



Fig. 81. 



is attached to the box and is divided into degrees, although only the 10° 

 divisions are shown at B. B and C are respectively the horizontal and 

 vertical projections. The separation of the scale into two parts, which 

 was made necessary by its lowered position, is shown at e and /. The 

 slot g, which is also shown in C, is for the easy removal of the uicol 



t . V ... V, 



Fig. 82. 



from the carriage. The prism is rotated 90° and is lifted out, after the 

 entire carriage is taken from the tube of the Microscope, by the removal 

 of the screw v. D is an end view, showing how the plate m entirely 

 closes the upper part of the opening in the tube and prevents all reflec- 

 tion from the surface of the nicol. The lever c is shown at c' rotated 



through 90°. 



