During the 18th century, great efforts were made to develop a practical marine chronometer. John Arnold and Thomas Earnshaw, working on entirely different lines, developed the detent escapement, commonly called the 'chronometer escapement', Earnshaw's design being adopted by most makers since. In the modern form of spring-detent chronometer escapement the discharge pallet is just beginning to move the detent to the left. The locking stone will release the tooth of the escape wheel, allowing an escape-wheel tooth to fall on impulse pallet. As the balance's clockwise swing continues, the discharge pallet releases the gold spring, allowing the detent to be returned by detent spring in readiness to receive the next escape-wheel tooth on completion of the impulse. On the return swing of the balance, the discharge pallet is allowed past the detent by the gold spring. This is the only escapement action in the anticlockwise half of its cycle. The action is known as 'single-beat'. The chronometer escapement is even more detached than the lever; another great advantage is that the escape-wheel teeth and discharge pallet require no oil. Originally most makers mounted the detent on pivots, with a separate adjustable return spring. This system was used extensively by European makers during the 19th century, but the necessity of oiling the pivot holes was a disadvantage, and the detent and spring formed from one piece of steel is usually found in marine chronometers.