The Compass Microscope, 1700-1830
The "Compass Microscope" is named so because of the center hinge, reminiscent of a drafting compass. It was used during the 18th century for inspecting small opaque objects such as fauna or flora. To use the instrument, the user would mount the specimen with the stage forceps and locate it just opposite the lens. The silvered reflecting Lieberkuhn mirror focuses more light on the top surface of the specimen. These microscopes were very popular as pocket field aids for naturalists.
Compass Microscope Set, ca. Mid-18th Century (Inv. YG-21-004)
This is a typical early set of a brass compass microscope of the mid-18th century. It has a brass body with turned handle, sliding and pivoting specimen holder, with forceps and a live-box that opens on a screw hinge to hold small specimens. The microscope includes four varied Lieberkühn eyepieces, brass tweezers, one wood eyepiece, a small "talc box" cylindrical container holding mica cover discs.
This type of compass microscope appears in the popular book by Henry Baker (1698-1774), The Microscope Made Easy (1743), as a microscope for opaque objects. Using the compass microscope as a basis for the design, this microscope incorporated a hinged focusing system with a reflector or speculum that reflects light upon the object making it possible to examine opaque as well as translucent specimens. The parts and functionality are explained further in chapter VII, entitled "Of the microscope for opake [opaque] objects." Baker's book that popularized the microscope in the 18th century.
Small Folding Compass Microscope, ca. 1750 (Inv. YG-20-032)
The early type compass microscope seen here is exceptionally small, measuring altogether about 10 cm long. So far, this is the only example known to us. So far the maker and provenience of this exceptional instrument remain unknown.
Compass Microscope in a Pocket-Sized Etui, ca. Mid-18th Century (Inv. YG-21-005)
This is another version of the mid-18th century compass microscope, safely collapsing into a pocket-sized pouch (or "etui").
From about 1700, the case design with tightly packed instruments was very popular and was to endure for almost a century. Now dubbed etuis, they were originally called pocket magazine cases and were made in several forms and sizes. They were made for pocket nécessaire, namely, sets for personal grooming usually containing a mirror, tweezers, scissors, ear spoon, scent bottles and/or ivory toothpicks. They also became very popular for English drafting instrument sets, to include a compass with a set of inserts: pencil, ink points and expansion bar, dividers, a sector, parallel lines ruler and a scales ruler.
With this background, it was only logical to house pocket microscopes for fieldwork in such cases. From around 1700, the London instrument makers Edmund Culpeper and Edward Scarlett sold miniature screw-barrel microscopes in such etuis. Here we see a nice compass microscope that can be collapsed into such a pouch for convenient portability.
French Compass Microscopes, late 18th to early 19th Century
This group of late 18th century compass microscopes are often considered to be French. The more elaborated one (Inv. YG-21-006) features two lieberkuhns, each one having a different lens, which enable the examination of the object under different magnification. The other two (Inv. YG-21-008 and YG-21-009) are two other variations of this style. They come with ebony turned handles and wood or cardboard etuis.