Early Aquatic Microscope, ~1750
The 'Aquatic microscope' is of the type originally suggested by the Swiss naturalist Abraham Trembley (1710-1784) for his seminal study of the hydra, later to be materialized by John Cuff (1708?-1772?), microscope maker, for John Ellis (1707-1776), an Irish naturalist. Ellis was highly regarded by Carl Linnaeus (1707-1778), who called him one of the brightest stars of natural history. Ellis was elected FRS in 1754. In 1755 he published his work on on corals, translated into French the following year, which won him an international reputation. Ellis wanted a microscope of high portability which made it easy to follow the activity of the hydra and other small water organisms held on a watch glass on a microscope stage. The first model was made by Cuff for Ellis in 1752. The design became popular, and microscopes in various forms of this design were made in England and Europe. Later improvements to this design eventually included rack and pinion focusing instead of the overly simple push-fit focussing of the first models (see here). Later, Raspail changed the forward and backward motion of the arm carrying the eyepiece to a fine motion driven by a screw mechanism (see here). In 1832 Charles Darwin took with him an advanced form of the Ellis Aquatic microscope, made by Bancks of London (also represented in this collection), on his seminal voyage on board HMS Beagle.
This early form of the aquatic microscope is mounted on the rayskin-coated wooden case with center mount for the pillar, has Lieberkuhn lenses of different magnifications that can be screwed to the bar above the circular stage with specimen holder and convex mirror below.