Polarizing (Petrological, Mineral) Microscope, c. 1895
(mittleres Polarisationsmikroskop)
This microscope is signed
on the tube Seibert in Wetzlar. There is no serial
number either on the microscope or on the storage case.
The serial number most likely was on a magnification
chart, which is now missing. The microscope comes
equipped with two Seibert objectives marked III and 0
that are stored in a leather covered box, three
eyepieces (one lacking its lenses made that way for use
of the instrument, without optics, as a simple
polarizing apparatus), and for conventional microscopy,
an aperture stop holder with three stops. The
microscope features a substage polarizing condenser
with a removable top element (stored in the leather box
when not in use) that is focused using a lever
mechanism, a rotatable analyzing prism with graduations
that mounts above the various eyepieces, and a
centerable rotating stage calibrated in degrees.
Another, more elaborate,
Seibert petrological microscope of slightly later vintage
is also represented in this collection. A similar model of the same
vintage, but lacking a rack and pinion adjustment, was
also produced by the firm.
On the upper portion of
the tube is an inventory label from the Iowa State Teachers College. This
college was founded in 1876 as the Iowa State Normal
School. It was renamed the Iowa State Teachers College
in 1909. It is now known as the University of Northern
Iowa. This microscope was obtained from the estate of
Dixon L. Riggs who was a Professor of Human Anatomy at
the University of Northern Iowa until his retirement in
about 1980. It is reasonable to assume that Dr. Riggs
collected this old relic from the earlier years of the
institution.