How does Patrick O'Brian use imagery in Treason's Harbour?

Imagery:

"But a deep sadness remained, not easily driven away by company or even by music; a sadness accompanied by a determination to live hearty while yet he could."

"The sherbet came, frosted with the cold, and having drunk a voluptuous pint Stephen said 'Well, now, it appears that our intelligence was right about the galley's cargo but mistaken about its time of departure.'"