It emerged this week that Sir Harry Kroto, the UK's most vociferous campaigner for chemistry, is leaving the UK for America, the land where research money grows on trees. The surprise news will have disappointed many fellows of the Royal Society. With Lord May of Oxford due to vacate his Royal Society presidency next year, many were hoping Sir Harry would step into his shoes. According to tradition, to get the top job at Britain's most prestigious scientific society you must be of Nobel laureate standard, and Sir Harry, who won the Nobel prize for discovering Buckyballs, is one of a very small band of people who fit the bill. But his supporters say that it is altogether different kinds of balls that would make him a perfect president.