After Tom breaks into Injun Joe’s room at the Temperance Tavern and finds the man passed out on the floor (leading him to conclude that the place must be haunted by whiskey), he runs past Huck, telling him to run for his life. Twain uses hyperbole to capture Huck’s fear:
“Run!” said he; “run for your life!”
[Tom] needn’t have repeated it; once was enough; Huck was making thirty or forty miles an hour before the repetition was uttered. The boys never stopped till they reached the shed of a deserted slaughterhouse at the lower end of the village.
In describing Huck as “making thirty or forty miles an hour,” Twain clearly exaggerates. (Humans run, on average, around eight miles per hour.) This is one of many examples in which Twain uses hyperbole to increase the tension during the boys’ adventures, keeping readers entertained and curious about what is going to happen next. The figurative language also matches Huck and Tom’s imaginative inner worlds, where they believe all sorts of impossible things, such as the idea that pirates are attacking them or that Robin Hood has come to the rescue. It’s possible, Twain is suggesting, that Huck really believes he's running that fast, underlining the power of children's imagination.