The Commissioning of the Corpus Clock.

The Corpus Clock has been invented and designed by Dr John Taylor for Corpus Christi College Cambridge for the exterior of the college's new library building.

It will be unveiled on 19 September by Prof Stephen Hawking, cosmologist and author of the global bestseller, A Brief History of Time.

The £1 million timepiece, known as The Corpus Clock, has been commissioned and designed to honour John Harrison, who was famously the pioneer of longitude and inventor of the esoteric clock mechanism known as a grasshopper escapement.

The clock has been designed by the inventor and horologist Dr John Taylor and makes ingenious use of the grasshopper escapement, moving it from the inside of the clock to the outside and refashioning it as a Chronophage, or time-eater, which literally devours time.

Longitude and Navigation.

Longitude is simply the difference between the observer's local (sundial) time and the local (sundial) time at Greenwich, England. As any sundial shows, the earth turns at 15 degrees per hour (360 degrees per day), so this time difference is easily converted into degrees of the earth's longitude. Both local and Greenwich time must be known onboard the observer ship to determine longitude, so finding longitude is much more difficult than finding latitude. Either a marine chronometer or various astronomical methods may be used to determine these two times, and therefore longitude.

To utilize accurate clocks for the measurement of longitude while sailing the high seas was first proposed by Gemma Frisius, in 1530. Christiaan Huygens’ tried his pendulum clock as such a marine clock in 1664, and in 1675 invented a marine timepiece with his spiral-spring balance wheel, but ocean tests showed that these lacked the accuracy required for marine use. With a highly refined version, which had technical improvements including a remontoire and temperature compensation, John Harrison demonstrated the first sufficiently accurate marine chronometer in 1762. We therefore will start with Harrison’s contributions, and follow with the previous and subsequent history of the three main methods of longitude measurement.