The following extract
is from the Journal of the Royal Microscopical
Society, 1898 . It describes the original Berger
microscope.
Berger's New
Microscope. The novelty in this instrument
is entirely confined to the substage, and is intended
to meet the constructional difficulties involved in
adapting the adjustments (especially the fine) to
Microscopes used for high-power photomicrography.
Usually the strain on the fine adjustment caused by
the extreme length (and consequent weight) of tube is
a decided disadvantage. Herr Berger arranges so that
both his coarse and fine adjustment are independent
of the drawout. The Microscope is also suitable for
ordinary use. Fig. 98 gives a general view, fig. 99 a
vertical section, and fig. 100 a ground plan.
The oval-shaped piece B
is arranged as a handle, which affords a strong brace
between the fine adjustment path V (fig. 100) of the
micrometer work and the special hollow-cast standard
H (fig. 99). The fine adjustment differs widely from
the general form, and is fitted by means of a very
strong dove-tail shaped slide F, so hollowed out in
its upper part that it affords the requisite room for
the spiral spring W. The under part of F is pierced,
and conceals the very long nut for the
micrometer-screw M. Contact ensues between the
hard-tempered extremity of the micrometer-screw and
another also hard-tempered anvil-shaped steel piece
which is screwed into the lid D2, closing dust-tight
the under opening in the standard H. On the fine
adjustment slide F rests, very solidly screwed, the
gear P for the coarse movement. The aluminum tube T
(fig. 99). In order to avoid undue wear and tear of
the mechanism is connected in the usual way with the
tooth-rack by means of a copper companion piece Z
(fig. 100). The coarse adjustment follows the usual
models. The micrometer-screw is thus seen to be
packed away in the hollow stand for protection's
sake. It is completely sheltered from direct
hand-touch. It is turned by means of an endless screw
E (figs 99 and 100) which gears into the toothed
wheel S, working on the flange of the screw, and
carries the usual micrometer knob. By means of this
arrangement two conditions are satisfied: the fine
adjustment is slowed in the most desirable way
without the necessity of requiring from the
micrometer-screw too fine a motion, and the position
of the endless screw, so firm and safe in the
handle-like stand, renders even rough mechanical
operations entirely without effect on the fine
adjustment.
In order to avoid
injury to the micrometer-screw when the slide F is at
its extreme highest or lowest position, a special
protection arrangement, limiting the play of the
endless screw, is contrived for the fine adjustment.
As is seen from fig. 100, the endless screw E engages
another toothed wheel S, which is a nut working on a
vertical screw. This nut S2 comes into contact with
the upper or lower surface of the chamber containing
it before the fine adjustment slide F reaches the end
of its travel, thus preventing strain on that part of
the mechanism.