In scene 1 act 3 of Romeo and Juliet what does Mercutio accuse Benvolio in Juliet?

In scene 1 act 3 of Romeo and Juliet, Mercutio accuses Benvolio of being a coward and not fighting Tybalt. He calls Benvolio a "coal" and says that he is more afraid of Tybalt's sword than of anything else.