Copy letter, from Sir John Herschel to Philosophical Magazine, dated at Collingwood Contemporary copy in sender's hand, signed by sender. Attempts further clarification of the matter discussed in John Frederick William Herschel's 1864-12-20 to the P.M. Reiterates John Frederick William Herschel's recollection of a conversation between W. H. Wollaston and Humphry Davy, which John Frederick William Herschel had described in a letter [see John Frederick William Herschel's 1826-11-25 to Francis Baily] and which John Frederick William Herschel refers to in his letter of resignation to Davies Gilbert [see John Frederick William Herschel's 1827-6-27], which latter letter John Frederick William Herschel quotes. 12 February 1865