What are the motifs in Walker Brothers Cowboy by Alice Munro?

Memory and the past are recurring ideas in this story. The narrator introduces these themes in the opening section, which does not take place on the same day as the rest of the story. In this section, the narrator contemplates the timelessness of Lake Huron, which is near their home. She has a hard time imagining bygone times in the area and realizes what a short space in history each individual occupies.