I found an on-line version of Lloyd's, difficult to read, but I can decipher the distance intervals you quoted.

His work is dated 1856 and I would assume the data points he list are those that were in use by mariners on the river at the time.

We're now looking at two values, 211 miles vs. 222 miles, a 5% variation. I would doubt if one could arbitrate between the two at
present.

None the less, email be and I will pass on my contacts name, title and email address. I would prefer not to broadcast on the board.

Thanks for pointing out "Lloyd's Steamboat Directory and Disasters on the Western Waters" to me. It's quite a tome and I plan on
adding a copy to my library.

I might also be able to identify the Western water maritime disaster in which my wife's gggrandparents perished.

George Martin
ggmartin55@att.net