From Joule to William Hopkins, giving a detailed account of experiments undertaken on beeswax, with calculations. Joule says his experiments "may perhaps serve to throw some light on the alteration of the point of liquefaction by pressure." The letter describes a series of experiments to determine the specific heat of wax at different temperature and the heat absorbed as it changed from solid to liquid. It also considers the expansion of beeswax by heat using equipment previously employed by Joule and Lyon Playfair in their experiments on the expansion of salts. Joule concludes by saying his experiments "are worth repeating and with greater accuracy".
Hopkins worked James Prescott Joule and William Fairbairn in Manchester on experiments to determine the effects of pressures on the melting point of substances, which were reported to the British Association's Hull meeting in 1852.
Dated at: Acton Square, Salford.
Included with this item is a typescript article "A new J.P. Joule manuscript" by L.L. Ardern, describing the letter, and explaining that it was found in a copy of Henry Watts' translation of Leopold Gmelin's Handbook of Chemistry, at the Manchester College of Technology library [now part of the John Rylands University Library]. The article was published in Nature175, pp. 606-608 (2 April 1955).