What makes the narrator feel uncomfortable at the entrance to the try pots?

It is late in the evening when Queequeg and Ishmael reach Nantucket, and go to the Try Pots, owned by Hosea Hussey, the cousin of Peter Coffin. Two pots hang from a tree near the inn, looking like a gallows. The Try Pots serves chowder for breakfast and dinner, and is paved with clamshells.