In Charles Dickens' "Hard Times," Coketown is portrayed as a sort of industrial nightmare area. The book is written in the context of an England where a new, industrialized society is taking the place of the old agrarian one.
The river that runs through Coketown (along with a "black canal") has suffered from industrialization just as the people have. It runs purple with some sort of "ill-smelling dye" that is part of the industrial waste.
Dickens uses the landscape of Coketown and his descriptions of its people as a critique of the new society that has developed in England.
In the first book of Dickens's "Hard Times" Chapter 5 entitled 'The Keynote' the readers are presented with a grim description of the ecological disaster that is Coketown.
The river in Coketown is described in the following words:
"a river that ran purple with ill-smelling dye."
The dye is the chemical substance which is used to color the textiles which are being manufactured in Coketown. After the textiles had been dyed the excess dye would have been washed out and drained into the river thus not only discoloring and polluting the river but also the environment by its stink.