MICROSPECTROSCOPE 
131 
Two types of these Drawing Eyepieces are manufactured, 
one for use with the microscope in a vertical position, the other 
for a slightly inclined instrument. 
Since the prism forms an integral part of the eyepiece, changes 
in magnification must be made wholly by changing objectives or 
changing the distance from drawing board to prism. 
Microspectroscopes or Spectroscopic Oculars consist of direct 
vision spectroscopes as integral parts of microscope eyepieces. 
They are usually constructed after the Sorby-Browning pattern, 
using a compound direct vision Amici prism. These prisms 
consist of either three or five units, a prism of flint glass between 
two of crown glass, or two prisms of flint glass alternating with 
three of crown glass. This prism is mounted just above the eye 
lens of the ocular, while the slit of the spectroscope is placed in 
the plane of the diaphragm of the eyepiece. Usually a com¬ 
paring prism is provided, which, when in position, cuts off half 
the width of the spectrum and permits placing in juxtaposition 
with the spectrum of the material being studied, the absorption 
spectrum of a solution of known composition. The position of 
bands or the amount of the spectrum cut off is determined by an 
arbitrary scale; or by means of an Angstrom scale reading in 
wave lengths, projected upon the spectrum, or by means of some 
indicating device mo\dng the length of the spectrum, its position 
at any given point being indicated by a scale moved by a microm¬ 
eter screw. This last type is the only one of value to the chemist. 
The microspectroscope illustrated,^ Figs. 66 and 67, is pro¬ 
vided with a measuring device capable of yielding concordant 
measurements with a very fair degree of accuracy. The instru¬ 
ment consists of the cell or chamber K in which are housed the 
slit 5, the comparing prism p, a movable diaphragm d, and in the 
lower opening the field lens / of tjie ocular. A small opening O 
in the side of K permits light, reflected by the mirror m, to enter 
the prism p and thus yield a spectrum in juxtaposition to that 
obtained from the object under the microscope. The solution 
or transparent solid used for comparison is held before the open¬ 
ing 0 by means of the clamps CC. The knob P serves to swing 
1 Manufactured by W. & H. Seibert, Wetzlar, Germany. 
