Extract from the
Illustrated Price List of Microscopes for Sale by
T. H. McAllister Manufacturing Optician, No. 49
Nassau Street, New York 1876
T. H.
McAllister's
Professional
Microscope
Has been highly
approved by all who have used it, as it combines many
advantages not heretofore found in any but the
highest priced instruments.
The Professional
Microscope stands fifteen inches high when inclined
as shown in the engraving the base is of brass, with
uprights to receive the axis, upon which the body
inclines to any convenient angle. The body is of
brass, finely finished with extension
draw-tube.
The coarse adjustment
for focus is by a delicate watch chain, controlled by
a large milled head on each side of the tube; far
more efficient and precise than the majority of Rack
movements, and will readily adjust the focus for all
except the very highest magnifying powers. The fine
adjustment for focus is by a very delicate Micrometer
Screw acting directly upon the body of the
instrument, and moving the entire optical system
vertically; free from the irregular lateral movement
so often inseparable from an adjustment acting only
on the Objective.
The Stage is large and
steady, but at the same time thin, allowing facility
for extreme obliquity of illumination. To the upper
surface a Plate Glass Stage is attached, which can be
freely moved in a vertical or horizontal direction to
any desirable extent, and can also be revolved. The
motion of this Plate Glass Stage is so delicate and
simple, that many experienced microscopists prefer it
to the elaborate screw stage. A movement as minute as
1-12000 inch can be selected by it. A brass rest with
springs to hold the object, is clamped to it, but can
be removed in a moment, leaving a clean glass plate
for examination of recent anatomical preparations,
chemicals, or other substances which would injure the
usual Brass Stage. Beneath the Stage is a separable
collar carrying the Diaphragm, and also adapted to
receive the Polarizer, Parabolic Illuminator, and
other accessories.
The Concave and Plain
Mirrors are mounted with universal motion, and slide
on a jointed bar for direct or oblique
illumination.
The mounting for the
Objectives is made with the " London Society Screw,"
so that the Objectives of all first-class makers, can
be used with the instrument.