Final answer:
The phrase from 'To Kill a Mockingbird' leverages a simile, a literary device that compares conversation with sinking to the bottom of the ocean, to imply a deep, possibly overwhelming sensation.
Step-by-step explanation:
The phrase “Taking to Francis gave me the sensation of settling to the bottom of the ocean” from To Kill a Mockingbird is an example of a simile. A simile is a literary device used to compare two different things, often to add emphasis or evoke imagery, using the words 'like' or 'as' for the comparison. In this particular phrase, the sensation of engaging in a conversation is compared to the experience of sinking to the bottom of the ocean, implying a feeling of being overwhelmed or deeply engrossed.