Wordsworth always felt much more at home in the countryside than in the city. Yet one golden morning, as he was crossing Westminster Bridge in London, he was struck by the extraordinary beauty around him, which inspired him to take up his quill pen and start writing.
It's still early morning in London and the city hasn't quite woken up yet. In the absence of any life, there's a quiet, majestic glory about the place, a characteristic one would normally associate with the natural world. Yet, even as the city sleeps, it still has a life of its own. This epitomizes the attitude of the Romantics, in general, and Wordsworth, in particular, towards nature—seen as a living entity in its own right. Wordsworth extends that attitude towards the sleeping city.
Before the tugboats start sailing on the Thames, "the river glideth at his own sweet will." In other words, before the people of London have woken up, nature is already active and awake. Yet the city, like nature, has a life of its own, its own heart, so to speak. Wordsworth senses it, beating away quietly but insistently beneath every roof, every dome, and every chimney-pot.