The two phrases that convey unease in the excerpt are:
"with such an air of melancholy"
"the onlookers, sensing misfortune"
"with such an air of melancholy" - The use of the phrase "air of melancholy" suggests a mood or atmosphere of sadness or gloom. In the context of a ship approaching the harbor, this creates a sense of foreboding or unease, as it implies that there might be something wrong or distressing about the situation.
"the onlookers, sensing misfortune" - The phrase "sensing misfortune" indicates that the onlookers are picking up on signals or signs that suggest something bad might be happening. This contributes to a feeling of unease because it implies that there is a collective perception among the crowd that the arrival of the ship is not proceeding as expected, and there might be a potential problem or disaster.