What instruments we have agree The day of his death was a dark cold day. (5-6, 30-31)
Auden's language here seems to suggest all of the minor traditions and procedures that we use to measure someone's passing: the time, heartbeat, and other small significant details that we can determine. Latent in his phrasing, however, is the sense that there are things that can't be determined by our reason or technologies.
The provinces of his body revolted,The squares of his mind were empty, (14-15)
Yeats's body becomes its own city in this metaphor – a suddenly vacant space that seems, well, just a little bit eerie. Perhaps that helps convey the strangeness and suddenness of his passing. After all, empty cities don't appear all that often, do they?
The current of his feeling failed; he became his admirers. (17)
This poem consistently separates Yeats the man from Yeats's poetic work: the one ends, but the other survives and modifies with each new reader.