Slough.
Mar. 7
1833.
Dear Sir/
We propose to take our departure for the Cape <1> some time in the ensuing Autumn probably about the end of September or beginning of October – The papers then for once are right though how it could come to be thus publicly announced is more than I can understand. I shall take with me my 20 feet reflector & the 7 feet Equatorial and hope to lay in a good stock of nebulæ and double stars for home consumption.
There is something very remarkable about the non-continuity of the Electric discharge as connected with Muscular Motion. The contractions of the heart are most likely produced by the periodical unloading of some battery in the brain – but what is more to the purpose is, that muscular exertion through the mental effort by which it is produced is anom is, as we are conscious, continuous yet the contraction of the muscles themselves is perceptibly a succession of interrupted convulsions. In ordinary exertion this is unnoticed but in violent & long continued strains it at length grows obvious – In age it [illegible deletion] peeps forth in all muscular action.– Now put that & that together &c &c.
I should think your expt on the optical fixation of a moving body must be very curious & interesting – I can imagine how by a dexterous motion given to a mirror the reflected image of a moving body may be reduced to rest but that cannot be what you mean. Undoubtedly also a true Photometer <2> would be (if a manageable instrument) a great acquisition – And to say the truth, I have often considered wondered that being, as I am aware you are in possession of a number of curious & interesting things in optical science and taking on every branch of that subject views of no ordinary kind – you should not have embodied them in some more impressive & permanent form than you have hitherto thought it worth while to do.– I am very glad therefore that you entertain the idea of communicating some of them to the R.S. <3> in the form of a paper, and I hope when you have fairly begun doing so you will not leave off till you have added to our knowledge by a large stock of new facts and to our philosophy by a copious disclosure of principles. I am fully convinced that there is no field which promises anything like physical optics in the present State of Science, and that the mathematical part of it has already so far outstripped the experimental that the cry has to be raised for facts quite as much as theories – I mean facts of that definite numerical or geometrical character which will bear to be accurately reasoned upon. Of course you have seen the Account of Hamiltons extraordinary prediction <4> of the Conical refraction. Here is theory outstripping experiment with a vengeance –
In my banishment (for though self-incurred it will still be to a certain extent an exile) I shall feel much gratified by hearing from time to time of any of your proceedings in this line. At all events pray send me copies of your papers as they appear. Anything will reach me through my Brother in Law P. Stewart <5> – if addressed to No 65 Cornhill. I hope however to meet you at Cambridge at the Reunion, if you attend it
& remain Dear Sir yours vy ty
JFW Herschel
H.F. Talbot Esqr M.P.
31 Sackville Street
London
Notes:
1. Herschel remained on the Cape of Good Hope until 1838.
2. Any instrument that measures the relative intensity, or ‘candle power’ of light.
3. Royal Society of London.
4. Sir William Rowan Hamilton (1805–1865), Irish mathematician, in the third supplement to Theory of Systems of Rays (1832), suggested the presence of conical refraction. Two months later, Humphrey Lloyd, Professor of Physics at Trinity College, Dublin, verified the theory by experiment.
5. Peter Stewart, printer.