Expresses his great appreciation for informing JH of the honor being conferred by making JH a Knight Commander of the ancient and venerable order of Danneborg.

Asks HO if he can discover, without mentioning JH's name, what it might cost JH to be formally enrolled in Denmark for the honor he has received [see JH's 1841-6-20].

Thanks HO for his effort on JH's behalf [see JH's 1841-10-10], and then describes some of his photographic experiments.

Recommends awarding Royal Medal to [William Parsons] Lord Oxmantown for paper on large reflecting telescopes.

Reliability of measuring instruments used in scientific and public surveys. Approves George Peacock's suggestion to revise survey tables for use by non-scientist surveyors. Schools should teach only legalized systems of weights, measures, and money.

JH is captivated by science of photography. Has blundered onto 'Calotype leaving out [W. H. F.] Talbot's principal ingredient!!' [Note added by daughter Isabella Herschel:] Papa is in hurry. Greetings to family.

Replies to [?]'s questions about 'Mr. Bethune's suggestions' concerning terminology to be used for standards of weight and measure. Agrees with G. B. Airy that term 'land' should be used with 'land chain' unit.

Expresses reservations about Samuel Brown's work. Apologizes for delay in trying calotype; has done only some vegetable substance trials.

Explains the phenomenon known as the 'harvest moon.'

Suggests a resolution of a small amount of money having to do with the exchange of some chairs; also asks about a dining room table.

Is unable to come to London for the Standards Commission meeting and thus will also not be able to come to the dinner party. Encloses some recent photographs.

Insists on inclusion of all data and graphs in the publication of the accumulated magnetic observations, made as part of 'perhaps the very greatest scientific operation ... ever ... undertaken....' Urges that funding be sought from the government.

Provides examples to justify governmental support of various magnetic and meteorological observations. States that 'Terrestrial magnetism ... of all sciences of observation holds out the greatest present prospect of decisive reduction under ... exact theory.' Mentions work by N. L. Lacaille and Thomas Maclear at the Cape.

Advice for standardizing observations, to be given to the Physical Committee of the R.S.L.

Thanks WS for Pulkowa Medal. Problematic health and large family make visit to WS impossible. Mentions [Francis] Baily's hope of terminating 'Cavendish experiment.' Sends copy of 'Revision of Southern Constellations.'

Discusses a letter in which JH explains why JH cannot, as a British subject, accept the foreign order offered him [by the Danish king]. Asks HS to read over the letter and to decide how it should be delivered.

JH replies (to RS:HS 15.389) that neither JH nor his father held that the moon influenced the atmosphere, though JH does connect a full moon with a clear sky. [Eliza] Hamilton, sister of W. R. Hamilton, has published some poetry that is not well known, but deserving. Cannot accept foreign order.

Will not attend B.A.A.S. meeting at Plymouth. Invites AQ to visit, preferably before 29 July, the date of the meeting. Sends thanks to [P. F.] Verhulst for elliptic functions.

Discusses advantages and disadvantages of 24 versus 36 hour series in meteorological observations. R.S.L. officially endorses 24 hours, but AQ should continue 36 hours if best for him. Does not possess the Comptes rendus of French Institute and cannot therefore see No. 413. Will attempt to procure sight of it. Asks AQ to return [P. F.] Verhulst's work to him. Expresses respect for AQ's work. Asks for understanding if JH does not answer every letter promptly.

GA and JH are on a committee (with Thomas Henderson) of the B.A.A.S. to supervise the reduction of N. L. Lacaille's star observations; JH encloses a draft report.