Unable to be at Katers' home for dinner, but will arrive later. JH is pleased to find HK's and JH's measurements of Mars agree with those of JH's father, William, and compares these with some other measures.
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Unable to be at Katers' home for dinner, but will arrive later. JH is pleased to find HK's and JH's measurements of Mars agree with those of JH's father, William, and compares these with some other measures.
JH very upset at the government abolishing the Board of Longitude; has many questions as to what will happen now.
About the use of the collimator, together with some family news.
Sends the formula for finding the maximum diameter of the planets.
Asks for the use of an invariable pendulum and a clock from the Board of Longitude so that G. B. Airy and William Whewell can carry out experiments to measure the change in gravity and the mean density of the earth, in a Yorkshire coal mine.
Informs HK that JH intends to resign as secretary of the R.S.L.
Comments on a paper about differential calculus, prepared by Mr. Knight, which JH confesses he does not understand. Adds some astronomical observations JH made at Slough before leaving there, and noting the appearance of J. F. Encke's Berlin Ephemeris concludes with 'England is fated to lag in the rear of all her neighbours—at least in science.'
Collecting English observations of eclipse of 7 Sept. 1820 for H. J. Walbeck. Construction of object glasses.
Delivered R.S.L. resolution on 'Junction of French & English triangles' to François Arago. Arago alone will meet HK and T. F. Colby to finish triangles this summer. J. B. Biot will collaborate next year with HK on pendulum measurements.
Encloses JH's translation of J. J. Littrow's method of determining latitude by pole star. It already appeared in F. X. Zach's Correspondance astronomique.... Send Francis Beaufort's survey of Karamania coast.
Sends set of William Herschel's duplicated papers. Curious results 'examining the rings,' but bad weather has hampered experiments. Correction of spherical aberration. JH is using J. d'Alembert's Opuscules. Image of Alpha Lyrae.
Leaving town for a week. Will read [Francis Beaufort's] book after return. Delighted by 'two instances of good fortune' in one week at Union Place [HK's home].
Examine reflecting theodolite by [?] Schenk, now at Edward Troughton's. Arrangements for Madeira expedition. James South is willing to make observations there. 'Bowdich (the African)' is now at Teneriffe or Madeira and needs employment. William Herschel's health.
Encloses table of star declinations for 1815 and 1820, received from F. W. Bessel, who used different meridian circles for each year.
Thomas Young approved supplying [Richard] Copeland with two sextants and one mountain barometer.
'Our micrometer screws' are not in error. F. G. W. Struve's star measurements using Josef Fraunhofer's repeating micrometer agree well with JH's. So error must be in HK's observations.
Invites HK to dinner Saturday to meet James South and Alexis Bouvard.
Has found some errors in the sheets of computations HK sent. Lists these. Comments on astronomical work of [William] Richardson and on the reading of 'The repeal of the Longitude Acts Bill.'