Another instrument is shown in Figure 3 and it is the
simplest of the models described in this article. The microscope is signed on
one side of the limb "C. Kellner's nachfolger" and on the other "FR. Belthle
in Wetzlar, No. 895". It can be dated to 1864. In the 1866 price list this is
referred to as the "Kleines Mikroskop, Neues Modell".
It is 11.5 inches tall as shown in the figure. The square iron base is painted
black and has an attached short iron pillar that supports the main body of the
microscope. This model does not have any provisions for rotation about the
optical axis. The single sided concave mirror is attached to a short arm mounted
below the stage. The coarse and fine adjustments are constructed in an identical
manner as in the previous example. The square stage has an oxidized brass finish
there are no provisions for stage clips. Inset under the stage is a wheel with 6
apertures. The microscope has no provision for an additional substage apparatus.
This microscope was also found with its case and a number of objectives and
eyepieces. The objectives represented are numbers 1 and 3 signed "FR. Belthle"
, and a number 0 signed "FR B". The three eyepieces are numbered I, II, and
The final model is shown in figure 4. It is signed on one side
of the limb "C. Kellner in Wetzlar"and on the other "Belthle & Rexroth, No.
280". It dates from 1859. In the 1858 price list, this is referred to as the
"Mittleres Mikroskop IIa ". As shown, it measures about 12 inches in height. The
focusing adjustments are as already discussed in the descriptions of the other
models. This microscope is equipped with eyepieces I and II and the objectives
1, 2, and 3 which are signed "Belthle & Rexroth". Among the accessories is an
articulated arm with ball and socket joints that fits into a hole in the base
which might have held a stage condenser (now missing) or something else? Also,
there is a Nicol prism in a brass holder that mounts behind the nosepiece. In
contrast to some of the other microscopes discussed herein, this instrument does
not rotate upon its base, but instead has an upper rotating stage plate. Below
the stage is a rotating diaphragm with 7 apertures.
Overall, these microscopes were extremely well
constructed. The mechanical movements are still smooth and without lost motion.
Most commendable in each of these models was the incorporation of various
adjustments to the focusing mechanisms that could compensate for wear. Such
adjustments were usually absent in contemporary microscopes and in many that