ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
503 
Fig. 52. 
by which every quarter revolution is marked, and attention called to the 
changes visible. 
The limelight illuminator is shown in position for illuminating 
opaque objects, and a light from the mirror through coloured glass gives 
a good background for a 
variety of objects. 
The limelight apparatus 
shown is conveniently clean 
and devoid of smell, and 
gives out very little heat. 
It can be used for oblique, 
opaque or transparent illu- 
mination, and can be varied 
in intensity. It cons’sts of 
a diminutive limelight on a 
condenser stand, with an 
adjustable plano-convex lens 
in front. By varying the 
distance of the plano-convex 
lens in front of the limelight 
either convergent, divergent, 
or parallel rays can be ob- 
tained and projected in any 
direction. 
Fig. 51 shows the instru- 
ment in position to project 
an image of an object on a 
sheet of paper on the table 
for sketching ; the limelight 
being attached in the place 
of the mirror. 
Fig. 52 shows the ad- 
justment of the instrument 
in an inverted po&ition. A 
board is attached to the box, 
and two struts are applied ; 
the Microscope is then 
clamped to the upper part 
of the board, the feet fitting 
into corresponding notches 
in the board. This enables 
the observer to examine 
objects from beneath, whilst 
objects in liquids and tubes 
are seen free from cylindrical 
aberration by immersing the 
tubes in a cell shown on 
the table in Fig. 51. 
The interior of crystals 
or gems can be microscopically explored by immersing them in equally 
refractive liquids. 
