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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'.

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'.