DJ 15

From page 117...

"Pearl looked as beautiful as the day, but was in one of those moods of perverse merriment which, whenever they occurred, seemed to remove her entirely out of the sphere of sympathy or human contact. She now skipped irreverently from one grave to another; until coming to the broad, flat, armorial tombstone of a departed worthy--perhaps of Isaac Johnson himself--she began to dance upon it. In reply to her mother's command and entreaty that she would behave more decorously, little Pearl paused to gather the prickly burrs from a tall burdock which grew beside the tomb. Taking a handful of these, she arranged them along the lines of the scarlet letter that decorated the maternal bosom, to which the burrs, as their nature was, tenaciously adhered. Hester did not pluck them off."

Lets tear this apart...

"Pearl paused to gather the prickly burrs from a tall burdock which grew beside the tomb."
Chillingworth is the 'prickly burrs'. He stayed away from Hester, then came into the picture when Pearl was born. Hester took him off for dead; she had no clue where he was. He was 'beside the tomb'.

"Taking a handful of these, she arranged them along the lines of the scarlet letter that decorated the maternal bosom, to which the burrs, as their nature was, tenaciously adhered. Hester did not pluck them off."
Pearl brought Chillingworth to Hester. As in his nature, he stuck to her. Hester could not get rid of him.

Pearl and the scarlet letter, at this point, are one. They represent the same thing: Hester and Dimmesdale's unconfessed sin. The only proven reason for Chillingworth's presence is Pearl and the scarlet letter. He isn't here for Hester at all. He is here because they are here. In a way, he too symbolizes/represents Hester and Dimmesdale's unconfessed sin.