John McLean, Mathewson v. Clarke — Opinion of the Court
“ The supercargo is the agent of the owners, and disposes of the cargo and makes purchases under their general instructions on his own responsibility.But Mathewson was master and supercargo, exercising full powers over the vessel and cargo. He purchased and sold where he could do so to the best advantage; and for his entire services in this agency, and for the management of the ship, he was paid. Now, can an agent, thus acting for his principals, engage in a traffic on his own account? He buys for himself and his principals at the same market, and sells at the same. ”
