This letter introduced the system still in use (1871), which has been most beneficial to the manufacture.  On Sept. 11th I proposed that all trials begin in the first week of January:  this also has been in use as an established system to the present time.—­It was pointed out to me that a certain chronometer was affected by external magnetic power.  I remedied this by placing under it a free compass magnet:  a stand was specially prepared for it.  I have never found another chronometer sensibly affected by magnetism.—­In November and December I tried my new double-image micrometer.—­Between May 16th and Oct. 13th a fireproof room was constructed in the southern part of the quadrant room; and in November a small shed was erected over the entrance to the North Terrace.—­The position of the free Meridional Magnet (now mounted in the Magnetic Observatory) was observed at every 5 m. through 24 hours on Feb. 22nd and 23rd, May 24th and 25th, Aug. 30th and 31st, and Nov. 29th and 30th.  This was done in cooperation with the system of the Magnetic Union established by Gauss in Germany.—­The Reduction of the Greenwich Planetary and Lunar Observations, 1750 to 1830, went on steadily.  I had six and sometimes seven computers constantly at work, in the Octagon Room.—­As in 1838 I had a great amount of correspondence with Mr Baily on the Cavendish Experiment.—­I attended as regularly as I could to the business of the University of London.  The religious question did not rise very prominently.  I took a very active part, and have a great deal of correspondence, on the nature of the intended examinations in Hydrography and Civil Engineering.—­On the Standards Commission the chief work was in external enquiries.—­On June 6th I had enquiries from John Quincey Adams (U.S.A.) on the expense, &c., of observatories:  an observatory was contemplated in America.—­I had correspondence about the proposed establishment of observatories at Durham, Glasgow, and Liverpool.

“I had in this year a great deal of troublesome and on the whole unpleasant correspondence with the Admiralty about the correction of the compass in iron ships.  I naturally expected some acknowledgment of an important service rendered to Navigation:  but the Admiralty peremptorily refused it.  My account of the Experiments &c. for the Royal Society is dated April 9th.  The general success of the undertaking soon became notorious, and (as I understood) led immediately to extensive building of iron ships:  and it led also to applications to me for correction of compasses.  On Jan. 9th I was addressed in reference to the Royal Sovereign and Royal George at Liverpool; July 18th the Orwell; May 11th two Russian ships built on the Thames; Sept. 4th the ships of the Lancaster Company.