On the fourth day, while exploring the island, Huck is delighted to find Jim, who at first thinks Huck is a ghost. Huck is pleased that he will not be alone on the island but shocked when Jim explains that he has run away.
Sand is a noun.
A noun is a person, place, thing, or idea. Sand is a noun because it is a thing.
Man vs. Nature
The natural forces of the Earth are acting against him.