course it is merely Jim's overactive imagination and belief in superstition that leads him to conclude that a silly, childish prank was the activity of witches. It does however serve to introduce the important theme of superstition into the novel, which, as is made clear, both Jim and Huck are subject to, to varying degrees.

Superstition plays a big role in Twain's attempts to characterize people of the 1840's who are ignorant of the laws of science and nature.  As human beings, we often look for reasons why something happens or an explanation for an event.  We "knock on wood" to ward off bad luck and carry good luck charms to feel safe.  Superstitions come from cultures where old wives tales are often embedded in a way of life that tries to explain phenomena.  Although often coincidental, people will naturally make connections between signs they see and connect them to what happened after an event occurs.  For example, if you start to notice that every time you wear a particular pair of socks, you hit a home run, wearing the socks will become a superstition you feel brings you luck.

In The Adventures of Huckleberry Finn, many of the superstitions come from the black culture in the novel.  Jim believes in witches and a hairball that knows everything.  He warns Huck that bad luck will come because Huck handles a snake skin.  He believes that shaking out a table cloth after sundown will bring bad luck as well.  Huck believes that when he kills a spider by flicking it into a candle flame, he is destined to have something bad happen to him.  Ironically, Pap shows up and tries to claim Huck's money after the spider incident.

In the 1840's, people didn't know a lot about how the world worked.  In order to explain and predict what could happen, they relied on superstitious beliefs to guide them and to warn them.  Twain used superstitions in the novel to give an accurate, realistic account of what life was like during the time of his novel.  

Superstition serves as a metaphor for the rigid and arbitrary rules of society.

Superstition is a running motif in The Adventures of Huckleberry Finn.  It is used as an example of how the dogmatic ways of civilization can be nonsense.  Just as the superstitions have the basis, the prejudices also have no purpose or reason.

In chapter 4, Huck consults a hair ball to find out what his father’s plans are.

Miss Watson's nigger, Jim, had a hair-ball as big as your fist, which had been took out of the fourth stomach of an ox, and he used to do magic with it. He said there was a spirit inside of it, and it knowed everything. (ch 4)

Obviously, something does not have magic powers just because it was in the stomach of an ox.  For Huck to ask the hair ball for advice, and for Jim to give it to him, is just plain silly.  Is that any sillier than thinking a person can be owned because of the color of his skin?  Jim may use the hair ball, but he is not the only one who thinks it has powers.  In this case, Huck thinks it has powers, and Jim is more or less fleecing him.

There are other examples of superstitions used to hide a person’s true intentions.  When Jim and Huck find a dead man in the floating house, Jim tells Huck that looking is bad luck.  He really does not want Huck to know it was his father, and does not want him to see his father in that condition.  Huck is looking out for Jim.

For example, when Huck kills the snake and leaves it as a joke for Jim, the snake bites Jim even though it is dead. 

And he said that handling a snake-skin was such awful bad luck that maybe we hadn't got to the end of it yet. (ch 10)

Obviously, they have already had “bad luck” from handling the snake.  Huck’s juvenile prank could have seriously injured Jim.  Huck is more concerned with how Jim looks at the moon, because “looking at the new moon over your left shoulder is one of the carelessest and foolishest things a body can do” (ch 10).  Clearly, Huck has his priorities mixed up.

The use of superstitions is more than satire.  Twain is not just making fun of poor country folk.  He is explaining how human nature tends to attribute things for the wrong reasons.  When we can’t explain things, we make things up to make ourselves feel better.

Huck has a hard life as the novel starts, with little control over what happens to him and no parent figure he feels he can truly rely on. He has not been well educated and doesn't have much to fall back on to help him cope with a very insecure reality. As a result, he has developed a complicated system of superstitious rituals to help himself feel safe and secure in what has for him been an unsafe world. We can see as the story begins, however, that these rituals don't seem to be working very well. For example, when he is living with Miss Watson and everybody goes off to bed, he is feeling lonesome in his room. As he recounts:

Pretty soon a spider went crawling up my shoulder, and I flipped it off and it lit in the candle; and before I could budge it was all shriveled up. I didn’t need anybody to tell me that that was an awful bad sign and would fetch me some bad luck, so I was scared and most shook the clothes off of me. I got up and turned around in my tracks three times and crossed my breast every time; and then I tied up a little lock of my hair with a thread to keep witches away. But I hadn’t no confidence. You do that when you’ve lost a horseshoe that you’ve found, instead of nailing it up over the door, but I hadn’t ever heard anybody say it was any way to keep off bad luck when you’d killed a spider.

We can see from the excerpt above how anxious Huck feels at Miss Watson's, even about small matters, and how complex and well developed his system of superstitions has become. We know from this he is not casually superstitious but takes signs and portents seriously and tries to deal with them according to a system that may not be rational, but nevertheless offers him some semblance of control.

Another example of his superstitious nature is below:

One morning I happened to turn over the salt-cellar at breakfast. I reached for some of it as quick as I could to throw over my left shoulder and keep off the bad luck, but Miss Watson was in ahead of me, and crossed me off. She says, “Take your hands away, Huckleberry; what a mess you are always making!” The widow put in a good word for me, but that warn’t going to keep off the bad luck, I knowed that well enough. I started out, after breakfast, feeling worried and shaky, and wondering where it was going to fall on me, and what it was going to be.

It is interesting to note that as he floats down the river with Jim and develops a secure relationship with this father figure, Huck's reliance on superstitious rituals lessens.

Superstition is tied most closely to the character of Jim, though Huck also participates in discussions on this topic. The novel begins and ends with this theme, with Jim significantly attributing his freedom and wealth to a superstition he espoused early in the story. 

The first episode of the novel, in fact, deals with Jim's relationship to superstition. 

Jim was most ruined for a servant, because he got stuck up on account of having seen the devil and been rode by witches. (The Adventures of Huckleberry Finn)

Jim is a self-described expert on superstition and his stature in this regard is telling. For much of the novel, Jim is depicted as a fool (and Huck is also, to some extent). In his one area of expertise, Jim proves himself to be a person of faith but not of intellect. 

He does not rely, however, on his intellect. Jim instead relies on his faith and his faith rewards him in the end. 

Jim tells Huck it is his hairy breast that has made him rich again just as he had predicted on Jackson’s Island.

Huck, for his part, is ambivalent about superstition. He does not clearly believe or disbelieve. This ambivalence is very similar to Huck's relationship to conventional morality. Huck is not convinced that Jim should be subjected to slavery, but he is also not sure that society is wrong in this arrangement. 

This moral conflict Huck faces in the novel is symbolized by Huck's relation to superstition. Jim is not similarly conflicted internally. His conflicts are purely outward. He is a "calm soul" as belief, conscience and the like are concerned. This stance is rewarded, ultimately, and Jim is freed. 

As the novel ends, however, we have seen many instances where that faith could have led Jim to disaster or even death. 

Part of the significance of superstition in the novel comes in how it is used to define Jim's character. In the first third of the novel, Jim is presented as being deeply gullible, open to being persuaded by foolish ideas, and ready to believe that which is not true. 

We see this in Jim's espousal of superstitions and in his responses to Huck's tricks. Later we see a different, more incisive set of traits in Jim, but initially he is symbolized by his superstitious attitudes. 

Additionally, Huck is depicted as having doubts about all matters of faith, from superstition to religion. He does, however, attempt to believe or at least allow for the potential veracity of the claims of others in this regard. Yet he is naturally resistant to believing in anything beyond his own experience. 

An exception to this tendency in his character is his strange belief in a false version of history (a version that he recounts to Jim with great comedic effect). 

The ultimate import of Huck's relation to superstition can be seen in two ways. First, Huck's attitude is contrasted to Jim's. The two are quite opposite in matters of faith, yet they are bonded by something lasting that has no basis in religion or superstition. Second, Huck's development is related to ideas of faith and specifically to the idea of independence of thought. Huck's distance from convention and superstition marks his progress toward independence and maturity.

Mark Twain strove to make the characters in The Adventures of Huckleberry Finn real people who would be very recognizable by those who read his novel. The superstitions held to be truth by the characters reflected the beliefs and educational levels of those characters and of their real-life equals.

Many superstitious beliefs develop from an everyday event that is exaggerated as it is retold. Spiders would not have bothered a nature-lover like Huck. When Huck brushed a spider off his shoulder and it landed in a candle flame and burned, he truly believed that his killing of that harmless animal would result in something terrible. He follows the rituals to try to prevent the bad luck, but doesn't have much hope for their impact.

I got up and turned around in my tracks three times and crossed my breast every time; and then I tied up a little lock of my hair with a thread to keep witches away. But I hadn't no confidence.

Slaves used superstitions to attempt to make sense of their world, to provide explanations for things they couldn't understand or control and had no education to explain. When Jim acquired the hair-ball from the ox's stomach, this unusual item was assumed to have special powers because of its rarity. After Huck provided the money the hair-ball needed to talk, it told Huck's fortune to Jim.

Of course, the prediction is so vague and full of contrasts that it could be interpreted to accurately predict any outcome or future event. However, Jim's telling of the fortune included the comment that "You gwyne to have considable trouble in yo' life." When Huck discovered his Pa waiting for him in his room, he naturally thought of that prediction and considered that the hair-ball had been absolutely right.