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Compound achromatic travelling microscope

Maker

SWIFT & SON

Country

United Kingdom

Signature

Unsigned

Category

Microscopes

Optical 1

Compound

Optical 2

Achromatic

Size of the box (h x b x d)

12 × 30 × 9.5 cm

Size of the microscope (h x b x d)

27.5 × 15 × 15 cm

Inventory number

SM 24

Description

The microscope is kept in a leather case, lined with red velvet.
Folded out it has the common English tripod stand. Coarse adjustment is by rack and pinion, the body tube which has a draw tube, is in a sleeve as well. Fine adjustment is by means of a micrometer screw acting on the limb. There are a plane and concave mirror adjustable in a bracket. There is a simple stage with spring clips and below the stage an Abbe type condenser with its iris diaphragm and filter holder. The microscope has a double objective changer.
The microscope has a Huygenian eyepiece, type ‘4’, with a focal length of 25.52 mm and a magnification of 9.80×.
There are two objective lenses both signed ‘J. Swift & Son London’. One is a ‘1/2’, N.A. 0.50 with serial number 51854; the second one is a ‘1/6’, N.A. 0.85 with serial number 48124.
The objectives were investigated using the Bleeker microscope with a body tube of 160 mm, the ‘1/2’ with a 10× Huygenian eyepiece, the ‘1/6’ with a 5× Huygenian eyepiece.

Objective 1/2 1/6
Focal length (mm) 12.45 3.83
Magnification 140.57 177.1
Numerical aperture 0.46 0.66
Resolving power (µm) 1 < 1

The ‘1/2’ shows a lot of coma, it resolves the diatom Stauroneis phoenicenteron into dots.
The ‘1/6’ is spherically undercorrected, it resolves the diatom Pleurosigma angulatum into dots.

It is not yet clear if Swift & Son made this microscope.