Jane is writing on Wednesday, so the journey took place on Tuesday. The carriage journey began at the Bath Hotel in London at 7:30 a.m. This was James Austen's carriage, but family (including Jane) filled it, so James took the coach going to Canterbury leaving at 5 a.m. (yikes!). Per Chapman's notes (in the Le Faye edition of the letters), this "coach left the Cross Keys, Gracechurch Street, London, daily at 5 a.m., arriving at Dover (71 miles by this route) in 15 hours." A long ride, imo.

Jane rode w/ James's wife Mary and their two children James Edward & Caroline. (James's daughter Anna, by his first wife Anne, was staying at Southhampton w/ Mrs Austen & Cassandra). They arrived at Godmersham at 6 p.m., which was 10.5 hours on the rode -- for less than 70 miles.