How does the author use foreshadowing in The Mound Builders?

When a writer drops clues about what is going to happen in a story—especially clues to unhappy or evil events—those clues are said to foreshadow future events. In The Mound Builders, Wilson leaves no doubt from the very beginning that the play is going to end unhappily. One of August's first lines in the first scene is a reference to "the wreckage of last summer's expedition," and audiences who have seen Wilson's earlier play The Hot l Baltimore know that the slide of the bulldozer in the first scene foreshadows future destruction.