Petrographical (Petrological) Microscope. Stand LC, c. 1902
The following was extracted from the Bausch & Lomb Optical
Co. 1904 Catalog:
Bausch & Lomb Petrographical Microscope
Base: horseshoe form, finished in our permanent bright
black finish. Pillar, finished same as base. Stage,
circular, revolving, with vulcanite stage plate, having
scales graduated in millimeters at right angles for the
location of the specimen, spring clips, circumference
graduated to 360 degrees, with vernier; centering
Substage: a modification of our complete substage, with
rack and pinion adjustment for vertical movement.
Arm: polished brass, extra long, giving increased
distance between optical center and base of arm.
Focusing adjustments: coarse adjustment by standard
rack and pinion; fine adjustment by standard micrometer
screw movement, having pointer and graduated milled
head of extra
large size& Fine adjustment has& dust-proof collar. Adjustment
of Bertrand lens by rack and pinion.
Main tube: with society screw, slots for quartz wedge
and Bertrand lens, sliding prism box, iris diaphragm
between prism box and Bertrand lens, draw tube
nickeled, carrying standard size eyepieces. Nosepiece
with centering adjustment.
Polarizing Apparatus: The polarizer
and analyzer are extra large Nicol prisms. The
polarizing prism is carried in revolving mounting with
pointer and silver circle graduated to
360 degrees. Directly above the prism is a
divisible condenser for convergent light.
By an ingenious device the upper lens of the
condenser can be instantly thrown to one side without
disturbing any of the adjustments. (See outline drawing
of condenser.) An iris diaphragm is mounted below the
polarizer mounting to modify the light.
Polarizing prism is carried in sliding prism box in the
main tube, so arranged that it can be thrown into the
optical axis of the instrument when polarized light is
desired, or thrown to one side when the microscope is
used in ordinary work.