Diagrams, speculum and polishing machine by unknown artist Plates 20-21, figures 1-9 showing a large speculum and a polishing machine used in Parsons' experiments using his reflecting telescope. Figures drawn separately and pasted onto backing sheet. An ink inscription verso reads 'Lord Oxmantown'. Not signed. Subject: Scientific Instruments / Astronomy Published in Philosophical Transactions as part of paper titled 'An account of experiments on the reflecting telescope' by William Parsons. Received by the Royal Society on 9 May 1840. Read 18 June 1840. [1840]