Joseph Priestley's microscope made by Benjamin Martin at the New Invented Visual Glasses, Fleet Street, London, with its receipted bill to Priestley dated Sept. 15 1767, complete with all accessories 33 items.

This microscope with accessories was purchased by Joseph Priestley in 1767 from the instrument maker Benjamin Martin (1704-1782) for the sum of £5 15s 6d.

Priestley referred to the use of a microscope in his work on photosynthesis. He observed that air whose quality was impaired by putrefaction, breathing of animals or burning of candles was restored by green matter which grew in water. This was seen to be vegetable in nature by William Bewley (1725-1783) who showed that it "came most properly under the denomination of the Conferva", Priestley himself recording "My own eyes having always been weak, I have, as much as possible, avoided the use of the microscope".