"How the chimney sweepers cry....palace wall".- explain

This stanza is borrowed from the mystical pre-romantic poet William Blake's 'London' taken from 'Songs of Experiences' which deals with the social evils of 18th century English life.
       
        Here the poet , William Blake, is extremely critical of the callousness and unconcern of London towards the poor and helpless sweepers of the chimney. He is sympathetic and the compassionate to the miserable state of the chimney sweepers and the soldiers who have  sacrificed their lives for the sake of society.

   These lines bring out Blake's humanism which is one of the salient features of his poetry. These lines clearly demonstrate Blake's soft corner for the downtrodden,destitude and deprived sections of the society.