Factual error: The problem with firing a cannon on steam power is to have the boiling water build enough pressure inside the barrel, with no leaks or openings to release it before its time. The professor's scarf and the plug hammered into the fuse hole (which also flies off just before the shot) wouldn't be good enough as pressure restrainers.
Factual error: Barbara takes an ancient document out of a filing cabinet. One of the words in its title is HIFTORIE, for "history." The old-fashioned way of writing the letter "s" was the so-called long s (ſ), not the letter "f", and this was only ever used as a lowercase letter. So the word would have been written as HISTORIE.