The Tripod Microscope of the 18th Century, Early Forms

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Edmund Culpeper's tripod Microscope ~1725 - 1730

 

Between 1725 and 1730, British microscope designer and maker Edmund Culpeper (1670 - 1737) produced what was to become a very popular microscope type. His design had a double tripod base; the lower level had a mirror to illuminate specimens on the upper level. He marketed it as the "Double Reflecting Microscope." Numerous makers quickly copied the design and enjoyed immense popularity throughout the 18th century.

The microscope was designed as two tripods standing one on top of the other at an offset of about 60 degrees, with the lower tripod standing on a round lignum vitae base topped by the round brass stage, and above the stage is the second tripod and above it the optical tube with the lens system. Focusing of the microscope is done by sliding the optical system, created from pasteboard coated with green vellum with gilding and lens mounts from lignum vitae coated with lacquer, into a cylinder from pasteboard coated with painted and polished shagreen. The main innovations that Culpeper introduced were the installation of a concave mirror on a vertically and horizontally rotating mount in the center of the base, which allowed light to penetrate transparent specimens and the installation of a fixed "bull's eye" condenser on a pivot at the edge of the brass stage. These innovations were groundbreaking and influenced how compound microscopes were made during the 300 years that have elapsed.

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The Culpeper microscope was marketed and stored in a typical pyramidal wooden box reminiscent of the metronome boxes of our time. These boxes became the standard that was later carried over to Cuff microscopes as well. At Culpeper's, the accessory drawer was at the bottom of the box. On top of it, Culpeper's trade card was affixed to the back of the box with his logo - two crossed daggers, and around it was the selection of scientific instruments that Culpeper marketed.

Culpeper's microscope suffered from the usual problems of pre-achromatic microscopes. The magnifications were low, and the lighting was weak due to the need to reduce using a diaphragm with a hole in the objective key to reducing the spherical aberration. The optical system, which at this stage included only three lenses: eye lens, body lens and bone lens, provided an image with significant chromatic distortions. But the primary role of this design was in its innovations and in expanding the popularity of the microscope among a wider public.

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There is no doubt that Culpeper's microscope was a significant breakthrough in the design and marketing of the compound microscope of the early 18th century. Beyond the functional design, which survived (with changes) for an entire century, the tripod microscopes were cheap to manufacture compared with previous models, they were impressive to look at (a significant factor since the microscope was also a social and class instrument throughout the 18th century) and relatively simple to operate. Manufacturers who copied Culpeper's microscopes (see below) placed the two tripods on top of each other without offset, turned the base into a box with a drawer for accessories, and later in the century moved to make the microscope out of brass.

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Matthew Loft's attributed tripod Microscope ~1730 - 1740

 

The unsigned Culpeper-style tripod microscope seen here is commonly attributed to Matthew Loft (1697–1747) of London. Loft was an apprentice of Thomas Gay between 1711 and 1720. In 1720 he established his workshop at the Golden Spectacles on Threadneedle Street, near the Royal Exchange. Loft made microscopes, telescopes, drawing instruments, and slide rules. A brass tripod microscope he made for Dr. Demainbray, tutor to George III, is of particular interest.

This version of the tripod microscope had three single-piece bowed legs screwed to diamond-shaped plates on an octagonal dyed oak base, unlike Culpeper's original design and Scarlett's somewhat later form. According to Clay and Court (1932), an earlier type with ornamental ridges and a later type lacks them. Therefore, the microscope in this collection is of the first type. Clay and Court based the attribution of this version of the Culpeper microscope to Loft on several examples of this model having in their accessory drawers printed labels stating: "Matthew Loft Maker at the Golden Spectacles, the Northside of the Royal Exchange, LONDON." A good example is MHS No. 54074. But other identical microscopes often have other makers' names. Good examples are SML 1993-1107, signed by John Cuff and A233310, signed by Thomas Wright. In reality, it is clear today that none of these makers produced their microscopes entirely. Like many 18th-century manufacturers, they probably acquired them by outsourcing their parts to numerous workshops and then retailing them under their name (which only appeared as trade cards glued to the inner parts of their pyramidal cases). Therefore, Clay and Court's assignment of this type to Loft seems groundless, as indeed claimed by Turner (1989). Consequently, we should refer to these names as retailers rather than makers.

In some ways, the Culpeper microscope was a step back in microscope design. The upright aspect was difficult to use and illuminate, and their optical performance was mediocre at best. However, the Culpeper-type microscope was simple to construct and not exceptionally costly. Therefore, it opened up the world of microscopy to a larger audience.

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