Final answer:
The selected passages primarily utilize the past tense, with occasional shifts to the present tense to create immediacy or highlight ongoing actions. The importance lies in the author's intentional and consistent use of tenses to shape the reader's experience.
Step-by-step explanation:
The passage in question utilizes both the past and present tenses. The past tense is used to narrate events that have already occurred, which is a common tense for storytelling. The present tense is sometimes used to provide a sense of immediacy to the narrative, making the reader feel more connected to the unfolding events.
For example, in the excerpts provided, the sentences 'By and by a drowsiness overcame him, and Venters began to nod, half asleep, with his back against a spruce.' and 'Venters surmised this much of the change in him...seemed remote and hard to recall; the difficulties and perils of the present' mainly use the past tense to describe actions that took place before the current moment in the narrative.
However, the narrative occasionally shifts to present tense, as in 'Venters listened.' This switch often occurs to describe ongoing actions or to highlight particular moments that are happening as the story is being told. It's important for writers to choose their primary tense carefully and stay consistent throughout their story, changing tense intentionally when appropriate to indicate shifts in time or to enhance storytelling.