Excellent - would recommend it to any reader of Larry McMurtry's "Lonesome Dove", for which it was possibly a source. Same trek from Texas to Montana and same time period.

Quite interesting.
For history buffs, Fitzroy was the captain of the Beagle, which took Charles Darwin on the 5 year cruise that lead eventually to the Theory of Evolution. Fitzroy was an early advocate of weather forecasting - for which, of course, he was ridiculed in the British Press.