“The Mural Circle was now nearly ready in all respects, and it was known that another Assistant would be required.  Mr Richardson (one of the Assistants of Greenwich Observatory) and Mr Simms recommended to me Mr Glaisher, who was soon after appointed, and subsequently became an Assistant at Greenwich.—­On Dec. 24th I have a letter from Bessel (the first I believe).  I think that I had written to him about a general reduction of the Greenwich Planetary Observations, using his Tabulae Regiomontanae as basis, and that this was his reply approving of it.”

1833

“On Jan. 4th 1833 my daughter Elizabeth was born.—­I prepared an examination paper for Smith’s Prizes as usual.—­On Jan. 5th I received notice from Simms that he had received payment (L1050) for the Mural Circle from the Vice-Chancellor.  About this time the Circle was completely made serviceable, and I (with Mr Glaisher as Assistant) immediately began its use.  A puzzling apparent defect in the circle (exhibiting itself by the discordance of zenith points obtained by reflection observations on opposite sides of the zenith) shewed itself very early.  On Feb. 4th I have letters about it from Sheepshanks and Simms.—­On Jan. 17th I received notice from F. Baily that the Astronomical Society had awarded me their Medal for my long inequality of Venus and the Earth:  on Feb. 7th I went to London, I suppose to receive the Medal.—­I also inspected Sir J. South’s telescope, then becoming a matter of litigation, and visited Mr Herschel at Slough:  on Feb. 12th I wrote to Sir J. South about the support of the instrument, hoping to remove one of the difficulties in the litigation; but it produced no effect.—­Herschel wrote to me, from Poisson, that Pontecoulant had verified my Long Inequality.

“Mar. 12th is the date of the Preface to my 1832 volume of Observations:  it was of course distributed a few weeks later.—­In my Report on Astronomy I had indicated the Mass of Jupiter as a subject requiring fresh investigation.  During the last winter I had well employed the Equatoreal in observing elongations in R.A. of the 4th Satellite.  To make these available it was necessary to work up the theory carefully, in which I discovered some remarkable errors of Laplace.  Some of these, for verification, I submitted to Mr Lubbock, who entirely agreed with me.  The date of my first calculations of the Mass of Jupiter is Mar. 1st:  and shortly after that I gave an oral account of them to the Cambridge Philosophical Society.  The date of my Paper for the Astronomical Society is April 12th.  The result of my investigations (which was subsequently confirmed by Bessel) entirely removed the difficulty among Astronomers; and the mass which I obtained has ever since been received as the true one.