Thanks Elwyn. That's very interesting, and sounds more likely.
I shall have to do some investigating to see if the dates fit. I did not know about the Grand Canal at all so this is a big help. Thank you.
Rando
Have done a little digging. The Athy Heritage Centre website says the link to Dublin from Athy opened in March 1791 and the journey time was 13hours, or less if 'fly boats' were used. This has to be the answer, so thanks for the pointer.