144 
ELEMENTARY CHEMICAL MICROSCOPY 
Klein’s Orientating Apparatus,^ Fig. 75, consists of a glass cell 
C to which a conical tube T is attached into which is ground a 
plug or stopper S. To the outer end of this stopper is fastened a 
metal head M, whose circumference is graduated, each diYision 
being equal to two degrees. These graduations are not intended 
for accurate measurement, but merely to serve as a guide in rotat¬ 
ing the material cemented to the knob k at the inner end of S. 
For use the cell and stopper are placed in a metal mounting B 
and laid upon the stage of the microscope. The cell C is filled 
with a liquid of such refractive index as to practically obliterate 
the usual heavy black contour bands. Leakage is prevented by 
Fig. 75. Klein Orientating Apparatus. 
holding the stopper tightly in place by the tension spring t. A 
curved finger, fastened by the screw A, holds the glass parts in 
the metal mounting and allows easy removal for cleaning. An 
index mark i upon the tube T furnishes a means of determining 
the amount of rotation of the object attached to k. The instru¬ 
ment is provided with two cells, one 10 millimeters deep and one 
15 millimeters deep, and a special condensing lens K for observa¬ 
tions with converging polarized light. 
A Simple Device for Orientation, often perfectly satisfactory, 
consists in cementing the object to the point of a needle or 
tiny glass rod and inserting the other end of the needle or rod 
into a mass of plasticine. The needle or rod can be moved in 
any direction and secured in place by gentle pressure of the 
fingers upon the plasticine. Solid angles of tiny crystals may 
’ Manufactured by Voight and Hochgesang, Gottingen, Germany. 
