Quote 7
"We can't ever tell the right time, and besides this kind of thing's too awful, here this time of night with witches and ghosts a-fluttering around so." (25.91)
Considering that Tom and Huck are so young, and that their knowledge of the world is so limited, their belief in strange, otherworldly things is understandable – also, in this case, ghosts and witches provide Huck with a perfect reason to stop digging a hole late at night, an unenviable task if there ever was one.
Quote 8
"My! I never once thought of it, Huck!"
"Well, I didn't neither, but all at once it popped onto me that it was Friday."
"Blame it, a body can't be too careful, Huck. We might 'a' got into an awful scrape, tackling such a thing on a Friday."
"Might! Better say we would! There's some lucky days, maybe, but Friday ain't." (26.4-7)
Here again, superstition gives Huck and Tom the opportunity to delay what is, no doubt, a scary endeavor – they go off and pretend to be Robin Hood instead.
Quote 9
"It [Injun Joe's ghost] would hang round the money. I know the ways of ghosts, and so do you."
Tom began to fear that Huck was right. Misgivings gathered in his mind. But presently an idea occurred to him –
"Lookyhere, Huck, what fools we're making of ourselves! Injun Joe's ghost ain't a going to come around where there's a cross!"
The point was well taken. It had its effect. (33.58-61)
In order to bolster Huck's confidence, Tom trumps one with another. Though they do believe in the craziest things, their system has some order to it.