This question is based on General Literature Principles and Literary Appreciation.
'Beautiful Kareendi, flower of my heart. No one but you can type them. For I want to send them care of the address of your heart, by the post of your heart, to be read by the eye of your heart, thereafter to be kept within your heart, sealed there forever and ever.'
The dominant device in this extract is
The extract addresses "Beautiful Kareendi" and builds a chain of parallel phrases: "care of the address of your heart, by the post of your heart, to be read by the eye of your heart, thereafter to be kept within your heart, sealed there forever and ever." The phrase "your heart" recurs in each successive clause, and each repetition adds a new dimension - addressing, posting, reading, keeping, sealing - creating a cumulative, escalating effect.
This is progressive repetition: the deliberate reuse of the same key word or phrase across successive clauses, with each instance advancing the idea one step further. The repetition of "your heart" is not static; it moves forward through a sequence (address, post, read, keep, seal), building emotional intensity with each iteration until it reaches the finality of "sealed there forever and ever."
This is not bold contrast (there are no opposing images set against each other), not progressive amplification in the strict sense (amplification involves restating an idea in increasingly grand terms, whereas here the same phrase is repeated in a chain of different actions), and not primarily rhetorical emphasis (emphasis would involve strategic stress on a single point rather than a sustained chain). The dominant device is progressive repetition - the rhythmic, forward-moving reuse of "your heart" that gives the passage its incantatory power.