[Diamond18]

As they approach the Marshes:<P> <BLOCKQUOTE>quote:<HR> Before the shadows of evening were long in happier lands, they went on again, always on and on with only brief halts. <HR></BLOCKQUOTE><P> <BLOCKQUOTE>quote:<HR> They had come to the very midst of the Dead Marshes, and it was dark.<HR></BLOCKQUOTE><P> <BLOCKQUOTE>quote:<HR> Presently it grew altogether dark: the air itself seemed black and heavy to breathe.<HR></BLOCKQUOTE><P> <BLOCKQUOTE>quote:<HR>Sam looked back and found that Frodo had lagged again. He could not see him. He went some paces back into the darkness, not daring to move far, or to call in more than a hoarse whisper. Suddenly he stumbled upon Frodo, who was standing lost in thought, looking at the pale lights.<HR></BLOCKQUOTE><P> <BLOCKQUOTE>quote:<HR>At last they came to the end of the black mere, and they crossed it, perilously .... It was late in the night when at length they reached firmer ground again.<HR></BLOCKQUOTE><P>So it's basically evening into night, and Tolkien reiterates the actual darkness and feeling of darkness throughout.