Before revision: The chronometer The clockwork in John Harrison's H4 marine chronometer In response to the problems of navigation, a number of European maritime powers offered prizes for a method to determine longitude at sea.
After revision: on display at the Royal Observatory, GreenwichThe chronometer The clockwork in John Harrison's H4 marine chronometer In response to the problems of navigation, a number of European maritime powers offered prizes for a method to determine longitude at sea.