See in text (Text of the Poem)
The image of the bog completes the frog metaphor introduced two lines prior. By characterizing the public audience as “an admiring bog,” the speaker devalues it. A bog, after all, is a section of spongy land, full of stagnant water and decaying matter. The idea is that any attempts at self-aggrandisement or posterity one might throw to the world will end up in a bog—going nowhere, rotting.