As Charlotte Doyle is only a young girl, she needs a responsible adult on hand to make sure she gets safely aboard the ship that's to take her across the Atlantic from Liverpool in England to Providence, Rhode Island. That particular role is filled in this instance by a man named Mr. Grummage, a business associate of Charlotte's father.
The ship in question is the Seahawk, an American merchant vessel. It's skippered by a Captain Jaggery, a name so infamous that the very mention of it causes a porter to refuse to go aboard ship with Charlotte's trunk. He makes it abundantly clear that he'll have nothing to do with Jaggery, “Not for double gold”.
A second man does the exact same thing when he finds out where Charlotte's trunk is supposed to go. Once he sets eyes on the bad ship Seahawk, he dumps her trunk and runs off without so much as a word of explanation. This is despite the fact that he'd been paid two shillings by Mr. Grummage.
In case we didn't already know it, there's something not quite right about the Seahawk. Both the ship and its captain obviously have a very bad reputation; just how bad Charlotte will soon discover for herself.