Le Roy designs the isochronous balance spring In 1766, clockmaker Pierre Le Roy completed manufacture of a chronometer featuring a detached escapement, a temperature compensated balance, and an isochronous balance spring. His design of an isochronous balance greatly improved upon the standard balance-spring design by Robert Hooke and Christiaan Huygens (which the two men created independently of one another in 1670). Le Roy had discovered that the balance would be isochronous when it was a specific length (and only that length). It was this isochronous balance spring that allowed his chronometer to achieve the greatest regularity possible, equivalent in efficiency and accuracy to John Harrison's groundbreaking H4 timekeeper. The H4 chronometer is widely regarded as Harrison’s masterpiece. Image Credit Pierre Le Roy. 18th century painter, anonymous, Public domain, via Wikimedia Commons
