The name of the author is the first to go
-- Speaker (Line 1)

Importance: This self-aware opening line is arguably an example of meta-poetry. It suggests that Collins himself may be the first thing to disappear from the reader’s mind. This implies that the work he creates, and by extension any work of art, is by nature ephemeral.

the memories you used to harbor / decided to retire to the southern hemisphere
-- Speaker (Lines 5-6)

Importance: This use of humour equates memories to elderly people who have left the workplace behind and moved to warmer climates. The word “harbor” enhances this image, suggesting that those memories were once sheltered at the very edge of consciousness. The memories then “decide”, making a conscious choice of their own over which the speaker has no control.

It has floated away down a dark mythological river / whose name begins with an L
-- Speaker

Importance: This is a reference to the river Lethe. In Greek...