The Advertisement to 1819, dated 20 December 1818, concludes with this paragraph:

I do not know which of the few scattered poems I left in England will be selected by my bookseller, to add to this collection. One, which I sent from Italy, was written after a day’s excursion among those lovely mountains which surround what was once the retreat, and where is now the sepulchre, of Petrarch. If any one is inclined to condemn the insertion of the introductory lines, which image forth the sudden relief of a state of deep despondency by the radiant visions disclosed by the sudden burst of an Italian sunrise in autumn on the highest peak of those delightful mountains, I can only offer as my excuse, that they were not erased at the request of a dear friend, with whom added years of intercourse only add to my apprehension of its value, and who would have had more right than any one to complain, that she has not been able to extinguish in me the very power of delineating sadness.

Lines 56-112 survive at the Huntington Library as part of Mary S.’s transcript for the printer (HM331; see MYR iii 113-20), so her jnl entries for 18-19 December, ‘write out Shelley’s Poem … Finish Copying his Poem’ (Mary Jnl i 244-5) probably refer to this poem, or to R&H, or to both, as the volume’s other contents were already in England. The date of the Advertisement was presumably the date of despatch to Oilier. The poem itself is dated pointedly in the title, October, 1818’.