Hooke's Microscope
Note the
improvement over Spallanzani's instrument of a generation
earlier. Illumination is by means of a candle flame reflected
by a concave mirror (K) through a water-filled glass
ball at left (C) that cools & focuses light at the
point of observation (M),
where the specimen is held by a
clip (I). Focusing is done by adjusting a screw (G), which allows
finer adjustments than in the earlier instrument. The optical
system remains crude.
