Photograph, universal joint from specula by unknown artist Photographic print showing the universal joint holding the tube of Parsons' specula. The photograph was published in the paper as an engraved figure. Subject: Scientific Instruments / Astronomy Published in Philosophical Transactions as 'On the construction of specula of six-feet aperture; and a selection from the observations of nebulæ made with them'. Received by the Royal Society on 5 June 1861. Read 20 June 1861. June 1861