My aunt sent me a link to a maritime history site that had searchable newspaper extracts. I was able to track down another website with archived images from one of the newspapers, where I found this ad in the Daily British Whig (17 June 1871, page 2, column 6).
There’s no way to know which Captain Couvrette was piloting the Union. It could have been Louis Charles or his (I am presuming) brother, George, who was also a boat captain.
I have spent weeks concentrating on Louis Charles and Philomene’s family group. I haven’t even begun to investigate laterally, so Captain George Couvrette will have to wait until I get the time to untangle Louis Charles’ siblings and figure out who was who.
My aunt also uncovered evidence of some Couvrettes settling in the Red Lake area of Minnesota (Joseph Couvrette appears to have married a native woman named Mari). That wouldn’t be far, geographically, from the Crookston area, where Louis Charles finally settled. I have no idea where the relation between Louis Charles and Joseph is, but there is sure to be one. That’s another puzzle to add to the To Research list.