What does Stubb observe about Ahab during the day before the crew assembles for Ahab's speech?

Stubb learns that inscrutable as Ahab might be, "he has that that's bloody on his mind." In Chapter 29, Stubb encounters Ahab at night on deck. Ahab has taken to pacing the deck after the others have gone to sleep; his ivory leg makes a ghastly sound on the deck that the sleepers below can hear. Stubb asks Ahab if he might wrap a rag around the end of the leg, to make it quieter....

Stubb learns that inscrutable as Ahab might be, "he has that that's bloody on his mind." In Chapter 29, Stubb encounters Ahab at night on deck. Ahab has taken to pacing the deck after the others have gone to sleep; his ivory leg makes a ghastly sound on the deck that the sleepers below can hear. Stubb asks Ahab if he might wrap a rag around the end of the leg, to make it quieter. Ahab does not appreciate this:

“Am I a cannon-ball, Stubb," said Ahab, "that thou wouldst wad me that fashion? But go thy ways; I had forgot. Below to thy nightly grave; where such as ye sleep between shrouds, to use ye to the filling one at last.—Down, dog, and kennel!”

Stubb takes exception to being called a dog, but Ahab is so menacing that he retreats below decks. 

I don't well know whether to go back and strike him, or—what's that?—down here on my knees and pray for him? Yes, that was the thought coming up in me; but it would be the first time I ever DID pray. It's queer; very queer; and he's queer too; aye, take him fore and aft, he's about the queerest old man Stubb ever sailed with.

Ahab's "queerness" extends to Stubb's dreams. In Chapter 31, "Queen Mab," Stubb tells Flask of a dream he had about this incident, in which a "badger-haired old merman" explains to him that to be kicked by Ahab is an honor. Stubb is willing to rationalize Ahab's conduct towards him to avoid conflict. Ahab is a frightening figure. He tells Flask that, odd as his dream might have been, it has made a wise man of him:

“D'ye see Ahab standing there, sideways looking over the stern? Well, the best thing you can do, Flask, is to let the old man alone; never speak to him, whatever he says.”