SUMMARY OF CURRENT RESEARCHES RELATING TO 
(594 
The accessory apparatus on the optical hank are, the condensing lens 
L which makes light-proof connection with the lamp, the heat-absorption 
apparatus F, and the two iris 
diaphragms, one between F and 
M, and the other between L and 
F. As regards the centering of 
the apparatus, the height above 
the table of the positive carbon 
for mean adjustment is first de- 
termined. The centres of the 
two iris diaphragms are then 
brought approximately to the 
same height. The axis of the 
condensing system has then to 
be adjusted. For this purpose 
the iris diaphragms are brought 
near the ends of the optical bank, 
one on each side of the con- 
denser. One of them is then 
illuminated from behind by a 
lamp, and the condensing system 
is displaced until the image of 
one diaphragm falls in the plane 
of the other. The condensing 
system is then adjusted so that 
the image is concentric with the 
aperture of the diaphragm. By 
interchanging the positions of 
the diaphragms, they can be 
brought to exactly the same 
height. 
The arc lamp is then brought 
into its place and connected with 
the condensing system. Its posi- 
tion is regulated by adjusting 
the screws so that the light 
passes centrically through the 
two diaphragms. The axis of 
the Microscope has then to be 
brought into the same direc- 
tion. For this purpose the condenser cf the Microscope is removed, 
but its iris diaphragm retained. The base-plate is adjusted until the 
light passing through the diaphragms on the bank falls centrically on 
the diaphragm of the Microscope. To determine whether the axis of 
the Microscope is in the same straight line as the centres of the 
diaphragms, a low power, about 70 mm., is used, and a piece of ground 
glass is fitted on to the eye-piece end of the body-tube. The Microscope 
diaphragm is then opened to its full extent, but those on the bank to a 
few millimetres only. The latter are then displaced until a sharp 
image is formed on the glass. The position of this image is adjusted by 
turning the base-plate about its axis. 
Fig. 100. 
Fig. 101. 
