I 'm in the midth of writing a very overdue review of Mary Beard's The Roman Triumph. In the book, she mentions that Gibbon, "as a prelude" to his "Decline and Fall," wrote an essay, "Sur les Triomphes des Romains."
I did some googling, and finally it showed up, in the original French and the English translation at Google Books, in Miscellaneous works of Edward Gibbon, Esquire, Volume III, Dublin 1796
Written in Rome in 1764, it is – to me at least – a fascinating treatise. (It's not easy to read physically, but if you switch to Full Screen, you can enlarge it.)
The other two volumes:
Miscellaneous works of Edward Gibbon, Esquire, Volume I, Dublin 1796
Miscellaneous works of Edward Gibbon, Esquire, Volume II, Dublin 1796
