Charles Dickens worked with many complicated ideas and it is shown in Bleak House in more than one instance. These opening paragraphs show just some of the subtlety in his work. He manages to set the scene as well as set in motion the ideas that will be explored within the novel.
He describes London as a dirty, backwards place where it would not be a surprise to see a prehistoric creature prowling the streets - it is as muddy and unclean as if it were not the great city it is supposed to be. While it is dirty and muddy, this idea of uncleanliness extends further than the literal being dirty. It is an attack on the city, and Bleak House did very well in attacking London and what transpired within its walls in terms of government and social ideas. It shows something almost chaotic in the people 'slipping and sliding since the day broke (if they day ever broke)', and this chaos, again, shows what Dickens thought of the city. He talks of the London fog (or the London Particular) in the same way. It's a literal darkness, in that where there is fog there is a lack of light, 'black drizzle' and 'the death of the sun'. There is also a metaphorical darkness in that the city's physical bleeds into the mood and the life, where 'crust upon crust of mud' is added to daily, where dogs are 'undistinguishable' and 'horses, scarcely better'. This conjures a depressing and bleak picture of the city, a cycle that doesn't end because nothing is given the chance to be cleaned, the 'tens of thousands of other foot passengers' not given the chance to see cleanliness and light, or goodness.
Dickens blurs the lines of metaphor and metonymy to great effect. There is 'fog up the river' and 'fog on the Essex marshes', there are literal, and it carries on as such for a little while, until the switch comes with the fog being 'in the eyes and throats' and 'cruelly pinching the toes and fingers of his shivering little 'prentice boy on deck' to the metaphorical.