To Mary Somerville   [11 June 1831]

My dear Madam

I return your Proofs with whose perusal I have been I assure you highly gratified, with such [illegible] as have received. The only remark of much consequence is that opposite to page xii when, in the hurry of composition you have taken the circle for a limiting case instead of the parabola — Perhaps too you would see no objection against modifying the expressions in p. lxiii and lxiv something according to what I have marked.

The star I allude to as having entered on its 2d revolution is γ Corona, one of the most difficult of all the double stars to measure from its extreme closeness

The measures of it Stand thus

  • 1781 . 69 Position 3041′ my Father

  • 1802 . 69 359 40 (by two measures agreeing perfectly) &o

  • 1823 . 17 25 57 — South and myself

  • 1830 . 30 44 25 my own measure

  • 1831 . 31 51 41 &o

The two last measures appear decisive, but that I might make sure of my own exactness (in so very difficult a case) I requested Mr Dawes of Ormskirk who has an excellent telescope and knows how to uses it excellently, to measure the star which he did without knowledge of my results and his measure comes out as follows

1831 . 34 — 5046′

The apparent priority of date arises from mean epochs having been taken — the best observations in fact were nearly simultaneous with Mr. Dawes’.

The measure No 2 should I apprehend be diminished by 180 — a mistake in this point is extremely easy to commit in η whose two stars differ very little in magnitude.

I suppose it cannot now be long before the book appears. Pray let me request a copy if you have any [illegible] at your disposal as early as possible.

You will be happy to heat that Mrs H on Sunday presented me with a fine girl & is doing perfectly well.

With Compts for Dr S

am dear Madam

Yours very truly

J F W Herschel

Please cite as “Herschel2654,” in Ɛpsilon: The Sir John Herschel Collection accessed on 29 March 2024, https://epsilon.ac.uk/view/herschel/letters/Herschel2654