Stand by the Union by Oliver Optic

Christy looked at the stranger with astonishment, and he could not imagine who he could be. He had seen no such person on board of the Bronx or on the deck of the flag-ship. When the prisoners from the Magnolia had been brought on board, Christy had been too much occupied with other matters to bestow any attention upon them with the exception of "the dignified gentleman in black," who proved to be his uncle. He had had no curiosity in regard to them, and Mr. Camden had disposed of them at the rail.

The commander thought it very strange that there should be a person on board of the steamer, and especially in possession of his cabin, who was an entire stranger to him. He looked at the intruder, who was a stoutly built man of rather more than forty years of age, with his hair and full beard somewhat grizzled by age. He was dressed like a seaman in blue clothes, though he was evidently not a common sailor, but might have been the master or mate of a vessel.