 Clunies-Ross's workers were paid in a currency called the Cocos rupee, a currency John Clunies-Ross minted himself that could only be redeemed at the company store.On 1 April 1836, under Captain Robert FitzRoy arrived to take soundings to establish the profile of the atoll as part of the survey expedition of the "Beagle".To the naturalist Charles Darwin, aboard the ship, the results supported a theory he had developed of how atolls formed, which he later published as "The Structure and Distribution of Coral Reefs".