“During this Long Vacation I had one private pupil, Crawford, the only pupil this year, and the last that I ever had.  At this time there is on my papers an infinity of optical investigations:  also a plan of an eye-piece with a concave lens to destroy certain aberrations.  On Aug. 20th I went to Woodford to see Messrs Gilbert’s optical works.  From Aug. 13th I had been preparing for the discussion of the Greenwich Solar Errors, and I had a man at work in my rooms, engaged on the calculation of the Errors.  I wrote to Bouvard at Paris for observations of the sun, but he recommended me to wait for the Tables which Bessel was preparing.  I was busy too about my Lectures:  on Sept. 29th I have a set of plans of printing presses from Hansard the printer (who in a visit to Cambridge had found me making enquiries about them), and I corresponded with Messrs Gilbert about optical constructions, and with W. and S. Jones, Eastons, and others about pumps, hydraulic rams, &c.  On Sept. 25th occurred a very magnificent Aurora Borealis.

“I do not find when the investigation of Corrections of Solar Elements was finished, or when my Extracts from Burckhardt, Connaissance des Temps 1816, were made.  But these led me to suspect an unknown inequality in the Sun’s motion.  On Sept. 27th and 28th I find the first suspicions of an inequality depending on 8 x mean longitude of Venus—­13 x mean longitude of Earth.  The thing appeared so promising that I commenced the investigation of the perturbation related to this term, and continued it (a very laborious work) as fast as I was able, though with various interruptions, which in fact were necessary to keep up my spirits.  On Oct. 30th I went to London for the Board of Longitude meeting.  Here I exhibited the results of my Sun investigations, and urged the correction of the elements used in the Nautical Almanac.  Dr Young objected, and proposed that Bouvard should be consulted.  Professor Woodhouse, the Plumian Professor, was present, and behaved so captiously that some members met afterwards to consider how order could be maintained.  I believe it was during this visit to London that I took measures of Hammersmith Suspension Bridge for an intended Lecture-model.  Frequently, but not always, when in London, I resided at the house of Mr Sheepshanks and his sister Miss Sheepshanks, 30 Woburn Place.  My quires, at this time, abound with suggestions for lectures and examinations.

“On some day about the end of November or beginning of December 1827, when I was walking with Mr Peacock near the outside gate of the Trinity Walks, on some mention of Woodhouse, the Plumian Professor, Mr Peacock said that he was never likely to rise into activity again (or using some expression importing mortal illness).  Instantly there had passed through my mind the certainty of my succeeding him, the good position in which I stood towards the University, the probability of that position being improved by improved lectures, &c.,