ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 93 



the observer to produce an aperture of any desired size in any part of the 

 field. By its use the reflection of light from the objective-lens surfaces 

 into the observer's eye can be largely prevented. 



Microscopic Examination of Metals by means of Polarized Light.* 

 H. Hanemann aud K. Ended discuss the application of polarized light 

 in metallography, describe J. Konigsberger's apparatus for the observa- 

 tion of opaque bodies in reflected polarized light, and indicate by 

 examples how isotropic and anisotropic constituents of metals and alloys 

 may be distinguished. 



* Stahl. und Eisen, xxxiii. (1913) pp. 1644-6 (1 fig.). 



