94 
ELEMENTARY CHEMICAL MICROSCOPY 
employed) strike a reflecting mirror V made of stellite ” 
from which they are reflected to a reflecting prism mounted 
at the inner end of M whence they are reflected to the eye of 
the observer. For photography the tube M is pulled out a 
short distance, thus removing its reflecting prism from the tube 
T and allowing an unobstructed passage of the rays through N 
to the ground glass or photographic plate at G. Exposures 
are made by means of the shutter Sh. 
Since both the coarse adjustment F and the fine adjustment 
/ are attached to the stage support and not to the tube of the 
microscope, focusing the instrument cannot disturb the align¬ 
ment of the radiant. Fine focusing while looking upon the 
ground glass is accomplished by the Hooke’s key Ki attached 
to the fine adjustment. The milled head K2 serves to turn 
up the burning away carbons, should the arc break or become 
dim while observations are being made upon the ground glass. 
To prevent dazzling the eyes by the highly polished specimen 
a cap with black glass is provided to fit over the ocular of tube 
M. There is also furnished with the instrument a cap with a 
tiny central pin hole which fits over the tube M. This device 
enables the worker to quickly center the radiant with respect 
to the microscope. 
The full-sized opening (45 mm.) of the stage is cut down for 
use to 15 mm. by means of a transparent plate glass diaphragm. 
The microscope is normally supplied with square stage only, 
but a rotating stage can be attached when ordered with the 
instrument. The mechanical stage which has been adapted to 
the square stage is awkward, insufficiently rigid and unsatis¬ 
factory. 
No device for oblique illumination has yet been developed. 
Each instrument is accompanied by a small pamphlet giving 
directions for setting up the apparatus and centering the radi¬ 
ant. These directions are so clearly written that the veriest 
tyro should be able to properly manipulate the instrument. 
The Reichert-Holz Metallurgical Microscope^ The new 
model of 1920 embodies may unique features and many improve- 
1 Made by C. Reichert, Vienna, Austria, for the Holz Co., New York, N. Y. 
