In recognition of his work on South American geology, invertebrate research and particularly his work on Barnacles, Darwin was awarded the Royal Medal of the Royal Society and received it at their meeting on 30 November 1853. The excitement brought back illness and he resumed the water treatment. This time it was successful and his health improved. He finished the second volume of "Barnacles", completing almost eight years of work which had made him the world's foremost authority on the subject.