Christaan Hyugens


Christaan Hyugens was the authority and pioneer of marine timekeepers. He outlined many of their issues, including their susceptibility to temperature and the disruption of the pendulum’s swing by waves. He invented the spiral balance spring as an alternative to the pendulum.

Board of Longitude


Pirates and shipwrecks lead to detrimental losses in lives and money. The Board of Longitude was established by King Charles II to find a method that could identify one’s longitude at sea, and prevent such losses. (Inspired Harrison to create a maritime timepiece, or chronometer, and verified methods that worked).

Jeremy Thacker


Jeremy Thacker invented a new clock enclosed in a vacuum chamber. The glass house shielded the chronometer from changes in atmospheric pressure and humidity, while a pair of winding rods kept the clock ticking even while it was being wound up. (Prior to this addition, watches would lose track of time during winding)

Gridiron-grasshopper Clock

1725 - 1728

John Harrison developed the gridiron-grasshopper clock, which involved combining long and sort strips of brass and steel to counteract changes in temperature.

John Harrison


John Harrison, after learning about the Longitude Prize, began building. He succeeded in creating sea clocks that did not need lubricants, were friction-free, and had pendulums that could be used all season.

Harrisons' Timepiece Shown to Board of Longitude


Halley directed Harrison to Graham, since the Board of Longitude was then filled with mathematicians and astronomers. Graham endorsed Harrison’s timepiece to the Royal Society. Eventually, Harrison’s success drew the attention of the Board of Longitude.



H2 contributed a mechanism to ensure uniform drive, as well as improved resistance to temperature changes. It was fully supported by the Society, who praised it as being a winner for the Longitude prize.

Pocket Watch Introduced to Harrison


John Jefferys introduced to harrison a pocket watch, which inspired the H4 . The H4 was the smallest of of the H series, introduced the verge escapement to block/release the clock’s rhythm, and was recognized as a masterpiece of clock-building and the solution to the longitude problem.



The H3 introduced the caged ball bearings anti friction device, which is still used today in almost every machine with moving parts.