"About this time a circumstance occurred of a disagreeable nature, which however did not much disconcert me. Mr Ivory, who had a good many years before made himself favourably known as a mathematician, especially by his acquaintance with Laplace's peculiar analysis, had adopted (as not unfrequently happens) some singular hydrostatical theories. In my last Paper on the Figure of the Earth, I had said that I could not receive one of his equations. In the Philosophical Magazine of May he attacked me for this with great heat. On May 8th I wrote an answer, and I think it soon became known that I was not to be attacked with impunity. "Long before this time there had been some proposal about an excursion to the Lake District with my sister, and I now arranged to carry it out. On May 23rd I went to Bury and on to Playford: while there I sketched the Cumberland excursion. On June 5th I went to London, I believe to the Visitation of the Greenwich Observatory to which I was invited. I also attended the meeting of the Board of Longitude. I think it was here that Pond's Errors of the Sun's place in the Nautical Almanac from Greenwich Observations were produced. On June 7th I went by coach to Rugby, where I met my sister, and we travelled to Edensor. We made a number of excursions in Derbyshire, and then passed on by Penrith to Keswick, where we arrived on June 22nd. From Keswick we made many excursions in the Lake District, visited Mr Southey and Mr Wordsworth, descended a coal mine at Whitehaven, and returned to Edensor by the way of Ambleside, Kendal, and Manchester. With sundry excursions in Derbyshire our trip ended, and we returned to Cambridge on the 21st July. "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.