Sentence:  ... if they had not been lifted in the air by the enormous accident of a man of genius, the Dickenses, I fancy, would have appeared in poorer and poorer places, as inventory clerks, as caretakers, as <WSD>addressers</WSD> of envelopes, until they melted into the masses of the poor. 
Meaning of the word marked with <WSD> tags:  A person who addresses (applies an address to an object to be delivered to a particular location).