The Golub Collection microscope No. 38 is similar to a "Universal" microscope made by Benjamin Martin found in a private collection, and Martin's 1750 Universal microscope as described by Clay & Court, 1932.
Signed Benjamin Martin
Microscope No. 38 in the Golub collection
Benjamin Martin 'Universal" microscope was characterized by possessing an additional lens he called the "between-lens". This lens is placed distant from the primary objective lens, and is mounted at the attachment end of a long snout (as shown here). Clay and Court described the between-lens as being the "only real improvement" to microscope optics from the introduction of the field lens (by Monconys) and the objective doublets at the beginning of the 19th century. Martin added this lens to all of his microscopes after 1759.
The between-lens decreased spherical and chromatic aberration.
Lenses systems of the Martin Universal microscope:
A: Eyepiece (2 lenses)
B: Field lens
C: Between-lens
D: Objective lens
Geometry:
A-B = 5cm
B-D = 5cm
