2For the sake of readers who have no time to dive into the thing it would perhaps be well to give the following summary at the end of the memoir.3
‘The results arrived at in the present investigation may be summed up as follows:
1. The mutual attraction of an electro-magnet and a sphere of soft iron, when <both> are in contact, is directly proportional to the strength of the magnet, <or in> [other] words, to the intensity of the magnetizing current.
<2. When a> constant force opposed to the pull of the magnet is applied to the <sphere of> soft iron <and when> the distance between the magnet and <the> sphere varies; to hold this force in equilibrium, the strength of [the] magnet must vary as the square root of the distance.
3. When the strength of the magnet is maintained constant, the mutual attraction of the latter and a sphere of soft iron is inversely proportional to the distance between them.
Combining the last two propositions we obtain:
4. The mutual attraction of an electromagnet and a sphere of soft iron, when both are separated by a fixed distance, is directly proportional to the square of the magnetic strength, or in other words, to the square of the magnetizing current.
I am well aware of the annoyance which all this must cause you – the additional expense which the alterations will render necessary supposing the memoir to be already printed I shall be most happy to bear – and with regard to your share in the transaction what can I do but assert my readiness to do you a similar kindness should you ever require it at my hand –
most faithfully yours | John Tyndall
Owing to the stupid manner in which library matters are conducted here I have not yet been able to see a <word missing> magazine [for] the present year. This has delayed my remarks on Mr Phillips investigations.4
<I was gra>tified today by the receipt of a letter from Dr Schlagintweit5 <I had> taken the liberty of making a few remarks on his memoir6 which, were he over sensitive, might have displeased him – The reverse however is happily the case | J.T.
The Editor of | The Philosophical Magazine | Red Lion Court | Fleet Street | London7
Monday. – 20 minutes ago I received your letter8 – I shall not attempt to thank you for it – it is too precious to me to be held in equilibrium by thanks – Yours was the second reply – I await the third,9 and shall let you know the upshot when all is decided. | J.T.
StBPL T&F, Authors’ letters
[8-10 March 1851]: dated by the postscript (Monday) and letter 0472. The Monday of the postscript, on which Tyndall received Francis’s letter (0472) of 5 March, was almost certainly 10 March, and the main part of the letter probably written Saturday, 8 or Sunday, 9 March. Thus, this letter was written immediately after, or is a continuation of letter 0473, dated 8 March. But, although it was written at almost the same time and requested further changes to the memoir on magnetism, the changes requested do not follow the same numbering system (although the order of requests match the text of the memoir) and the paper is a different size and folded differently. As we cannot establish with certainty that 0474 is a continuation of 0473, we assign independent numbers to these letters.
This entire manuscript is in very poor condition. It is yet another letter in which Tyndall requested changes to his memoir on magnetism, some guesses as to missing words can therefore be based on the published text.
the memoir: Tyndall’s memoir on magnetism (letter 0464, n. 2). An amended version of this summary is on p. 295. The most significant difference is the order of the four propositions. The order of the propositions here is the same as that in letters 0465 and 0466, although the wording is different, the wording of this letter being closer to that of the published paper. However, in the published version, the second and fourth propositions as listed here are switched, becoming the fourth and second propositions respectively. Letter 0475 is a fragment, listing Tyndall’s corrections on proof reading the memoir. It is plausible that he requested a change in order when proof reading.
Mr Phillips investigations: probably the papers on the electricity of steam in the Phil. Mag. alluded to in letter 0470 (n. 11). Tyndall had promised to read the papers for Francis, who doubted their merit.
Dr Schlagintweit: Hermann Schlagintweit. See also letters 0470, nn. 13 and 14, and 0498, n. 5.
remarks on his memoir: shortly after 19 February (letter 0470) Tyndall had written to Hermann Schlagintweit asking him to give place names in French rather than German. He indicates here that he had also proffered some critical analysis.
The Editor … London: address from outside of the folded sheet.
your letter: Tyndall referred to letter 0472, in which Francis offered career advice.
I await the third: Tyndall had requested advice from three friends concerning the advisability of returning to Queenwood College, and had previously received a reply from George Wynne (letter 0471).
Please cite as “Tyndall0474,” in Ɛpsilon: The John Tyndall Collection accessed on 27 April 2024, https://epsilon.ac.uk/view/tyndall/letters/Tyndall0474