How was Sir Simon finally laid to rest?

From the text:

There had been a great deal of difficulty at first about the inscription on Sir Simon's tombstone, but finally it had been decided to engrave on it simply the initials of the old gentleman's name, and the verse from the library window. The Duchess had brought with her some lovely roses, which she strewed upon the grave, and after they had stood by it for some time they strolled into the ruined chancel of the old abbey.

What happened with the ghost of Canterville at last?