English Passengers by Matthew Kneale

In 1857 when Captain Illiam Quillian Kewley and his band of rum smugglers from the Isle of Man have most of their contraband confiscated by British Customs, they are forced to put their ship up for charter. The only takers are two eccentric Englishmen who want to embark for the other side of the globe. The Reverend Geoffrey Wilson believes the Garden of Eden was on the island of Tasmania. His traveling partner, Dr. Thomas Potter, unbeknownst to Wilson, is developing a sinister thesis about the races of men.