THIS, the penultimate volume of Faraday's Diary, covers the period from November 1851 to November 1855. In the main, the topics treated are lines of magnetic force, the construction of a magnetic torsion balance and the measurements made therewith, electrodynamic induction in liquids and magne-crystallic action. The MS. of this section of the Diary is noteworthy as containing a number of ” the actual specimens prepared by Faraday in 1851 to illustrate the delineation of lines of magnetic force by iron filings. The filings were fixed on cartridge paper by means of gum water, sometimes mixed with a solution of ‘the red ferro-prussiate of potassa’ (apparently potassium/), which was found to leave a blue impression of the pattern after the filings had been removed or worn off”. A number of the specimens have survived the changes of more than eighty years, and this volume contains collotype reproductions of some of the more suitable specimens. The frontispiece is a reproduction of the famous painting which represents Faraday giving the Christmas lectures of 1855-56 before the Prince Consort, the Prince of Wales and Prince Alfred. Faraday's Diary: being the various Philosophical Notes of Experimental Investigation made by Michael Faraday, D.C.L., F.R.S.., during the Years 1820–1862 and bequeathed by him to the Royal Institution of Great Britain, Now, by order of the Managers, printed and published for the first time, under the editorial supervision of Thomas Martin. Vol. 6: Nov. 11, 1851–Nov. 5, 1855. Pp. xiv + 495 + 8 plates. (London: G. Bell and Sons, Ltd., 1935.) 7 vols., £12 12s. net.
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