Condenser
222
THE PROJECTION MICROSCOPE
[Ch. IX
I«
Fig. i2i. Projection Microscope.
1,2 Feeding screws of the arc lamp.
j Set screw for the upper carbon.
4 Set screw for holding the stem of the arc
lamp in the socket on block I.
5 Set screw for the lower carbon.
IIc+ The horizontal, upper carbon. It
must be made positive (+).
L The source of light, i. e., the crater of
the upper carbon.
IV— The vertical or lower carbon. It is
negative (—).
Axis, Axis, Axis The principal optic axis
from the positive crater of the arc lamp
extending through the condenser, the stage
water-cell, and the microscope to the screen.
1 Condenser 2 The triple condenser for
receiving and concentrating the light from
the crater of the arc lamp.
/ The first element of the condenser which
renders the diverging light parallel. It con¬
sists of a meniscus next the light and a
plano-convex lens (compare fig. 105, 111).
2 The second clement of the condenser
which concentrates the parallel beam.
W Water-cell between the two plano-con¬
vex lenses in the parallel beam of light.
As a projection microscope uses ob¬
jectives of shorter focus and smaller
diameter than the magic lantern,
greater care must be exercised in get¬
ting all the elements, radiant, con¬
denser and projection objective, cen¬
tered along one continuous line or
axis, and in having the different ele¬
ments the right distance apart.