The date range and the addressee are conjectured from CD’s residence in Down from September 1842 onwards (Correspondence vol. 2, Appendix II), and by the existence of other letters mentioning spermaceti to William Baxter or his son William Walmisley Baxter, the chemists in Bromley that CD used whenever he was resident in Down (see n. 2, below, and Correspondence vol. 26, letter to W. W. Baxter, 6 January [1878]).