"On the beam... [a] yellow bird... behind the rafter... her wings are spreading!"Abby claims to see a yellow bird, which is a supposed sign of witchcraft. In this scene Mary Warren gives in and joins the rest of the girls and their tale of witchcraft, instead of calling them out on their lie and defending Elizabeth.
"My niece, sir, my niece - I believe she has vanished [and Mercy Lewis]."Parris announces that Abby and Mercy Lewis have vanished, possibly to some boats that were leaving. This could show their guilt for making up something completely fake that in turn is the reason many people hung.
"It is as though they stood in a spinning world... half amazement... [as] he look[ed] at her incredulously."John and Elizabeth Proctor hadn't seen each other in three months, during which John was basically tortured. While talking to Elizabeth, John decides that he will confess to witchcraft in order to live.
"You have all witnessed it... I am not worth the dust on the feet of them that hang... show honour."John Proctor confessed to witchcraft, but wouldn't sign a written confession. He wouldn't dirty the names of those who hung as he would be saying that they are all liars and hung for no good reason, so he rips up his confession. By doing this he goes to the rope and supports all those that hung for their honest innocence and strong will.