The original title of the poem, written in 1900, was "By the Century's Deathbed." Thus the reference to "The Century's corpse" in stanza 2:
It was a cold, bleak winter day. And a cold and bleak time for the poet, too. The earth looked featureless and desolate as if entombed by the grey clouds above. The wind sang a sad and mournful song. Everything seemed dead and buried, no sign of life was stirring. And the poet was like that too: listless and lifeless.
In stanza 3, somewhere in the dark forest a sound was heard. It was a happy sound seemingly out of nowhere and surely unexpected. An old thrush began to sing in spite of the wind and cold. An act of hope, a call to better things perhaps, was heard in the distance.