To Harriet Moore   Saturday^{1, 2}

Harriet Moore: Harriet Moore (née Henderson, 1779–1866), widow of the surgeon James Carrick Moore (1763–1834), and mother of five children, among whom were Harriet Jane Moore and Julia Moore. The wealthy Moores had close connections with the RI and frequently entertained Tyndall at their Wimbledon home.

[19 March 1864]: although LT gave Saturday, 9 March 1864 as a date for this letter, there was no such date (9 March was a Wednesday that year). A more likely date is Saturday, 19 March 1864, a day after Tyndall lectured on ‘Contributions to Molecular Physics’ at the RI (see n. 3), and perhaps LT mistakenly wrote ‘9’ for ‘19’.

the lecture last night: on 18 March 1864, Tyndall delivered a Friday Evening Discourse at the RI, ‘Contributions to Molecular Physics’ (Roy. Inst. Proc., 4 (1862–6), pp. 233–40). Tyndall had given this as the Bakerian Lecture the evening before at the RS (J. Tyndall, ‘The Bakerian Lecture.—Contributions to Molecular Physics.—Being the Fifth Memoir of Researches on Radiant Heat’, Phil. Trans., 154 (1864), pp. 327–68; read 17 March 1864). Hirst noted in his journal entry for 20 March 1864 that in the RI lecture, Tyndall drew out heterodox conclusions ‘on the danger of ascribing motives to Providence—apropos of the beneficial effects of the vapourous envelope of the earth—and of the groundlessness of the fears that the investigation of truth in science should be injurious to religion’ (Brock and Macleod, Hirst Journals, p. 1666–7; also see Ascent of John Tyndall, p. 181). In the Chair at this RI lecture was Albert Edward (1841–1910), Prince of Wales, eldest son of Queen Victoria and Prince Albert (ODNB).

your kind daughter: a reference to either Harriet Jane Moore or Julia Moore.