Encloses [G. B.] Airy's letter, which he thinks should accompany [Humphrey] Lloyd's reply regarding magnetism. Thinks all Physical Committee members must be made aware of new developments.

Discusses term and extra magnetic observations with regard to [Humphrey] Lloyd's letter. Would prefer to keep them separate, but feels no harm will come from keeping them together.

About eclipse observations of 1842, together with JH's speculations about the existence of an atmosphere around the sun. Enclosed is an eclipse drawing by Francis Baily.

Stresses importance of development and phases of periodic phenomena on earth's surface. Magnitudes of stars are the only observations JH is doing. Asks for help in planning trip on continent for three of his daughters and their governess.

Thanks for assistance in preparing trip. JH's daughters will probably not stay in Brussels long. Mentions his first engraving for Cape observations of nebulae is to be engraved this very day. Three quarters of his reductions of the southern sweeps are completed.

Thanks for suggestion of gold plating the telescope mirrors. Mentions idea of mounting a reflector horizontally but finds its execution 'insufferable'. Thanks for work on photometric measurement of light of stars. Disagrees on some results. Encloses new photographic specimens.

Sorry that JH can only send 'very poor' photographic process specimens.

Agrees with suggestions made by ES concerning the publication of meteorological observations.

Unwilling to come to a meeting as JH anticipates the return of some of his children from the continent; seems considerable confusion as to who is to do what about star catalogues [see GA's 1841-7-27].

Compares actinometric measurements of radiation. Explains interest in total eclipse relative to actinometry. Discusses the possibility of making actinometric measurements by photographic means.

Proposes meeting times in town. Suggests that JF observe the upcoming total eclipse astronomically. Agrees with JF's seemingly 'cold &c' circular on scientific partnerships, while regretting that it needed to be written.

On RM's stepping down as president of Geological Society. Where exactly abroad will RM pursue enquiries?

Instructions for preparing liquid for the actinometer. Describes 'very strange' experiments on the spectrum as well as an 'unusual' cloud formation.

Clarifies role and methods of R.S.L. Council and scientific committees, suggesting that members of Physical Committee need to be better informed about its activities.

Discusses how exceptional observations of meteorological and magnetical phenomena should be recorded and what significance should be attached to them. Cannot attend next meeting of committee.

Sets up approximate meeting time, depending on his family's timely departure to Antwerp, with JF at the R.S.L. apartments.

Discusses JH's spectrometer and possibility of using surplus from R.S.L. Donation Fund for its construction and enquiry with it into nature of light and heat.

Is confident that by summer his sweeps will all be reduced and arranged in three catalogs for JH's Cape Results.

Met Friedrich Bessel at the Manchester B.A.A.S. meeting; invited him to Collingwood, where he expects Bessel in a few days. Enclosed with the letter a specimen of a new photographic process called 'Chrysotype.' Marvels at traveling from Hawkhurst to Manchester round trip (420 miles) in under 23 hours!

Reports the erection of an obelisk at Feldhausen to commemorate the site of JH's 20-ft. reflector. Back at Cape Town, Thomas Maclear is measuring N. L. Lacaille's Arc of the Meridian. JH received the Prussian Order of Merit.