The poem The Dust of Snow exposes the irrelevancy of superstition which are popular among us. It is commonly believed that crow is the sign of bad omen. It bring doom and mishap. Similarly, dust refers to death (in Christian and Islamic culture) and Hemlock tree (a poisonous tree) on the other hand was used by Socrates to commit suicide.
However ironically, all these things of bad omen make the poet’s day cheerful. So, the poem depicts that we should always hope for the best and never take anything as bad omen.