Sir George Biddell Airy (1802-1892) was the Lucasian Professor of Mathematics at Cambridge and Astronomer Royal from 1835-1881. In 1875 Airy introduced his famous auxilliary 'bar' which he used for the fine adjustment to the compensation of a conventional marine chronometer balance. He was able to insist that all chronometers, tested at the Royal Observatory and bought for use by the Royal Navy, were fitted with the bar he had invented. However certain balances, such as Kullberg's flat rim balance, could not be fitted with it so the stipulation was quietly dropped.