Clarification of Frankenstein?

If that is what it says, then that is what it means. It is FICTION. I doubt that Mary Shelley had the faintest idea of how fast an eagle could fly when she wrote it. It is a literary illustration, that is all. You are meant to enjoy the story, not analyse it in nit-picking detail. (And, sorry to disillusion you, but I think that the Baron did not REALLY bring a dead body back to life. That bit is complete fiction as well).