Harrison, John (1693-1776), an English clockmaker, developed a number of scientific instruments. In 1726, he made the first gridiron compensating pendulum, a pendulum that compensated for changes in length resulting from changes in temperature. Harrison incorporated the pendulum in a timekeeping device called a chronometer, and this improved chronometer enabled sailors to calculate longitude much more accurately than they had been able to before. Harrison was born in West Yorkshire, England.
