A suggestion I have come across is that it is a reference to the loss of the Steam Ship Arctic on 27th September 1854, en route from Liverpool to New York - accounts indicate that this had the same public impact as the loss of the Titanic half a century later: see https://poll.pollcode.com/93816625_result and https://www.thoughtco.com/the-sinking-of-the-steamship-arctic-1774002 .

And then a case I think of memory fading fast, but the song going on forever.

Progress provides for greater and worse disasters...