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St. Augustin - HC is 'now flourishing about in Paris'. He went to the Institut yesterday where his 'friend Biot' introduced him to, among others, Laplace, Delambre, Arago, Cuvier, Gay Lussac and Humboldt. It is a custom for the savants to have soirées one morning a week for their friends and strangers - Humboldt has offered to take HC to Laplace's tomorrow. He has gained entry into this elite circle thanks to a lady who talks Persian and brought letters of introduction to Humboldt, and through his own acquaintance with Thomas Edward Bowdich [famed for his travels into Africa] currently living in Paris.

Asks on behalf of M. Biot what is meant by supersedeas in Newton's 'otiore expensa'. He has written an article on Richard Sheepshanks for the Examiner; wonders who will have both power & leisure to help young observers now.

Invites Whewell to come to a meeting of the Institute.

Edinburgh - JDF thanks WW for all his support over the years and for his recent intervention in ensuring JDF's paper [On the Hot Springs of the Pyrenees and the Verification of Thermometers] was published in the next part of the Transactions of the Royal Society [see JDF to WW, 21 Sept. 1836]. In connection with the proceedings of the BAAS meeting at Bristol, JDF has 'got 12 Thermometers from 3 to 26 feet long, ready for the rites of sepulture'. One set are to lie in a 'warm bed of Trap' rock at the observatory, another in the 'hard cold sandstone of Craig Leith'; and a third set in the 'softly repose in a deep bed of perfectly uniform, dry, incoherent sand. How often do you think they should be observed?' JDF has subjected his magnetic observations taken at the Alps and the Pyrenees to calculation and has found a 'distinct indication of a diminution of intensity of about 1/1000 part, for 3000 feet of ascent'. Jean Baptiste Biot has written a very interesting paper about astronomical refractions. JDF hopes to apply Biot's methods to his observations with the actinometer on the extinction of light in the atmosphere. Has WW seen Lloyd's [Humphrey Lloyd] six lectures on the wave theory?: 'It seems to be done in a style much wanted as a model for English works of the kind'. JDF is really looking forward to WW's 'Opus Magnus' [The History of the Inductive Sciences, from the Earliest to the Present Time, 3 vols, 1837]. What does WW think of the Metropolitan University: 'will it have any effect upon Oxford or Cambridge? If it can hurt anybody it will be our medical schools. Has Murphy [Robert Murphy] got the London College Chair. He wrote to me for a certificate which I declined on the ground of insufficient acquaintance with his department of the Pure Mathematics'.

Has received the Correspondence of Sir Isaac Newton and Professor Cotes.

Thanks him for offering a copy of Correspondence of Sir Isaac Newton and Professor Cotes.

Edinburgh - JDF has not seen the experiments by Biot [Jean Baptiste Biot] on circular polarisation which WW gave an account of in his last letter: they 'must have been made subsequent to, and in consequence of mine'. WW is wrong to suggest to JDF that he has neglected the influence of the crystalline structure on heat: 'Depend upon it that Biot has not got the effects you mention, with Dark heat, and hence the information it gives is only partial, shewing that light and heat disappear together as they always do'. He has been investigating the action of metals on heat which show both remarkable analogies but also differences with light: 'P.S. Since writing the above I have (partly) a doubt which has much perplexed me. The action of metals gives a maximum polarizing angle for heat greater than for Light, whence I concluded that the index of refraction must be greater for the former than the latter, - contrary to my general views'. He finds in David Brewster's paper 'that a precisely similar fact occurs in the action of metals on light; the Red ray is polarized at a greater incidence than the blue'.

The Athenaeum Club - JDF has read an account of the BAAS Dublin meeting and Professor Powell's [Baden Powell] account of Melloni's [Macedonio Melloni] and JDF's experiments: 'His chief object seems to have been to make out the accuracy of his own papers, and he certainly mistakes Melloni's results as completely as it is possible to do when he makes him say that there are two distinct kinds of heat. On the contrary there are an infinite variety which pass into one another insensibly. He equally mistakes my results when he makes them to depend upon Mr Murphy's [Robert Murphy, Elementary Principles of the Theories of Electricity, Heat, and Molecular Actions, 1833] Integration. This is precisely Biot's [Jean Baptiste Biot] objection, viz that the two positions of the plates are not symmetrical as regards the effect of conduction [JDF gives a diagram showing the angles of the plates]. Granted at once. But will the mathematical gentlemen only have the goodness to see the experiment tried and they will see that the effect is of an order quite superior to any effect of conduction whatever - that it is independent of the distances of the plates from one another, which requires, no nicety of adjustment, so that the integration (if practicable) will go for nothing. I have really a right to insist that my experiments shall be seen before they are judged. I admit all the mathematical perturbations, but the chief cause is as clearly developed as the influence of the moon on the tides'. The tables have turned in Paris in favour of JDF's theory: 'Arago [Dominique F J Arago], Libri [Guglielmo Libri] and Dulong [P. L. Dulong] have taken up my cause, Biot is at last silenced'. Could WW point out to Mr Murphy [Robert Murphy] 'that in the case of Depolarization by the mica plate there is the most perfect symmetry (mathematically) which he can desire'.

Nantes - JDF spoke to Arago [Dominique F. J. Arago] about the tide observations - at least regarding those being made this month: 'he had represented the matter in the strongest terms in the Chamber of Deputies as you may have seen by the newspaper - he read an extract from your letter, and told the minister of Marine that what was doing in England put him to the blush, and quoted yours and Mr Lubbock's [John W Lubbock] Papers. With regard to the Brest observations he assures me that they are half-printed and going on'. JDF was not so successful regarding Arago's magnetical observations 'which I much fear he will never print'. Arago 'lives in a perpetual turmoil, in which science has no serious part, and yet he seems to feel that he was born for that and not for the petty concerns of daily objurgations'. Biot [Jean Baptiste Biot] attacked JDF's experiments on polarised heat 'in most unmeasured terms: this pleased JDF 'because it shewed how much importance he attached to them'. Biot regretted that JDF had not brought his apparatus with him so as to repeat the experiments: However, JDF offered to repeat them 'with the aid of a few bits of Mica to shew the chief results to Melloni [Macedonio Melloni, who argued that light and radiant heat are effects directly produced by two different causes]...This I did, and afterwards more at large to Mr Libri [Guglielmo Libri] who has taken up my cause very warmly and is perfectly satisfied'. JDF was astonished that even though Biot and Melloni attacked his experiments, neither of them 'had attempted to repeat one of the experiments'. There would have been a meeting at the Institute last week in which Libri was to defend JDF. The only person doing anything of value is 'as usual' Poisson, who is just bringing out his book on heat: 'I know of nothing else doing at the moment in Paris'. JDF has 'never seen anything connected with the origin of Gothic which appeared to me nearly so interesting as the Abbey of Fontevrault and the church at Candes'.

7 Camden Street - ADM has dislocated his shoulder. Regarding WW's inquiry concerning Galileo he has consulted Libri could not 'find the least ground for supposing that any pope had done anything...I feel confident that all the rumour is a mere sham'. Shares a story told by Biot to Libri, who quoted the Chief Inquisitor in Rome that he would not allow a professor at Sapienza university to teach the motion of the earth.

7 Camden St., Camden Town - M. Biot inquires for the meaning of Newton buying a supersedeas.