Nautical chronometers were of great importance in the 18th and 19th centuries as aids to navigation. Accurate measurement of time was needed for the determination of longitude. Earnshaw was not the first to make such chronometers, but he was one of the first to make them cheaply enough that they started to become essential equipment for a ship at sea. By the time the "Beagle" set sail, it was being reported in "The Nautical Magazine" that the price of chronometers was dropping rapidly while the same quality was being maintained. Earnshaws' chronometer had a novel escapement mechanism, the spring detent escapement, and a bimetallic strip for temperature compensation so that it would continue to maintain accuracy in all climates around the world.