Cal 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, hydr