The Scilly naval disaster of 1707, which claimed nearly 2,000 lives and was one of the greatest maritime disasters in the history of the British Isles, is attributed to the mariner's inability to find their longitude. This led to the Longitude Act to improve the aids available for navigation. Marine chronometers were as revolutionary in the 19th century as GPS is today. However the cost of these instruments could be prohibitive, sometimes resulting in tragic consequences for ships that were still unable to determine their longitude, as in the case of the "Arniston".