J. Y. Brinton, The Law of the Sea
“ The common carrier is one who offers to carry for all who may choose to employ him. The private carrier is one who transports by virtue of a special agreement. The private carrier appears more frequently in water carriage than in land transportation. Most ships, for example, carrying bulk cargoes by special arrangement are private carriers. Most passenger ships are common carriers of passengers. Ships carrying miscellaneous or package freight, and running over regular routes, are common carriers. ”
