Early Screw-barrel Microscope, No. 62

This instrument is an early, possibly Italian, screwbarrel microscope similar to the instrument invented in 1694 by the Dutch mathematician Nicolaas Hartsoeker. The microscope is essentially a simple magnifier with a threaded attachment that allows focusing by adjusting the distance of the sample to the objective. The first screwbarrel microscopes, like this instrument, had no handle. The user simply held onto the barrel of the microscope and looked through the objective (facing down in the image above). In 1702 the Englishman James Wilson added certain refinements, including a handle that made the microscope more convenient. An example in the Golub Collection of a Wilson-type screwbarrel microscope can be seen here. While screwbarrel microscopes were all simple magnifiers, a few opticians created screwbarrel microscopes with a double, or compound microscope attachments. The most famous of which was created by Edmund Culpeper. A fine example in the Collection of a Culpeper Screwbarrel double microscope can be seen here.

Instrument No. 62 is made of bone and a dark wood (probably Lignum vitae), and consists of only a few components. The central screw barrel is the condenser assembly, which had no lens or is now missing the original condenser lens. It is screwed into the turned bone barrel. The barrel has a large square cutout to accommodate the two flat bone sample holders, coiled brass spring, and the objective assembly. The sample, a folding animalcule cage or a glass phial, would be placed between the two flat holders. Focusing was accomplished by screwing in or out the condenser assembly, which would press the sample nearer or further to the magnifying lens. The objective consists of a biconvex lens mounted in a hardwood. This instrument has only one objective lens that sits in the base of the body and is removed easily. Wilson-type instruments came with six lenses that screw into the body, thus it is possible that this instrument also came with additional interchangeable lens assemblies. Imaging is good but shows considerable vignetting.

Featured 04/2011

Age: 17201750
Made by: Unknown
Made in: Possibly Italy
Objective lens