MICROSCOPES FOR USE IN CHEMICAL LABORATORIES 71 
are sent through the preparation upon the stage by means of 
the mirror M. The analyzer consists of a prism sliding in and 
out of the microscope 
tube at A. In the 
illustration the dotted 
lines indicate the ap¬ 
proximate direction of 
the light rays used to 
illuminate the object. 
When moderate tem¬ 
peratures are neces¬ 
sary the objective 
must be cooled by 
means of a blast of 
air directed upon the 
lower lens, and when 
high temperatures are 
employed the objec¬ 
tive must be water- 
jacketed. 
Binocular Micro¬ 
scopes. Greenough 
No laboratory 
which is concerned 
with problems involv¬ 
ing industrial micros¬ 
copy, or with the 
qualitative examina¬ 
tion of fragments of 
material detached 
from fairly large masses of matter, can be considered as satis¬ 
factorily equipped unless it includes a binocular microscope 
of the Greenough type. The marvelously long free working 
distance of the double objectives of these instruments, their 
remarkable penetrating power, the fact that the images of the 
object being studied stand out with stereoscopic distinctness 
and are right side up instead of inverted, the adaptability of 
Fig. 2g. Simple Form of Hot-stage Microscope. 
Polarized Light is obtained by Reflection from 
the Plates P and R and the Mirror M as indicated 
by the Dotted Arrows. A = Analyzer. B= Small 
Gas Burner which swings under the Stage Opening. 
