Attempts further clarification of the matter discussed in JH's 1864-12-20 to the P.M. Reiterates JH's recollection of a conversation between W. H. Wollaston and Humphry Davy, which JH had described in a letter [see JH's 1826-11-25 to Francis Baily] and which JH refers to in his letter of resignation to Davies Gilbert [see JH's 1827-6-27], which latter letter JH quotes.