Letter, from Henry Warburton to Sir John Herschel, dated at 45 Cadogan Place Autograph letter signed by sender. Discussed John Frederick William Herschel's proposed felspar paper [see Henry Warburton's 1816-4-24] with W. H. Wollaston. Suggests using Wollaston's and [recently deceased Smithson] Tennant's unpublished method to test for alkalis and give Tennant credit for it. James Smithson first coined term 'silicate'. 3 June 1816