Posted by: T. Boyd | May 9, 2009

Heavenly Clocks, Part 2

He reveals deep and hidden things;
He knows what is in the darkness,
and the light dwells with Him.

(Daniel 2:22 ESV)

Last time I wrote about how Galileo’s discovery of the moons of Jupiter led to accurate determination of time regardless of location.  The British Royal Astronomer, John Flamsteed, published the first tables of Jupiter’s moons in 1707, after Galileo had proposed the method 90 years earlier.

Although sailors had learned to determine latitude (N/S), an accurate time piece was needed for determination of the longitude (E/W).  You need time to the nearest minute to resolve the longitude within 17 miles (at the equator).  If you know the time to the nearest second, you can know your east-west position within 500 yards.The problem remains that it is nearly impossible on a moving, rolling deck of a ship to use a telescope to see the moons of Jupiter.  In addition the weather and the position of the planet in the night sky have to be just right to make an attempt.

Grasshopper escapement invented by John Harrison

Grasshopper escapement invented by John Harrison

Since accurate clocks were sorely needed for ship navigation, the British Parliament in 1714 offered three prizes up to 30000 pounds Sterling for determining longitude on a voyage to the New World. The book, Longitude, written by Dava Sobel is an exciting, suspenseful story about John Harrison (1689 – 1776) who spent most of his life producing a series of five clocks to fulfill the requirements of the prizes.

In 1761, Harrison’s 4th clock, which looked like a large pocket watch, was only 5 seconds slow at the end of a two month voyage on the HMS Deptford from England to Jamaica – an error in longitude of only one nautical mile!  Can you believe it?  But this astounding achievement was labeled “just luck” by Parliament, and the prize refused, even though the requirement was to measure it within 30 miles!

He repeated the feat in 1765; once again the prize was refused.  Finally, he appealed to King George III, who insisted that Harrison be given the prize.  In 1773, at 80 years of age, he was finally rewarded by Parliament – but not the official award, which apparently was never given to anyone.

Harrisons 4th clock that met the challenge

Harrison's 4th clock that met the challenge

(The H4 clock is running again – click to see the BBC News article)

Although John Harrison was denied the official award, seafarers from that time forward were able to navigate accurately. The designer and maker of the wonders and beauties of our cosmos gave a gift to this man so he could in turn create such marvelous time pieces.
I praise You, for I am fearfully and wonderfully made. Wonderful are Your works. (Ps. 91:14 ESV)


  1. I read the BBC News article – it was written in 2002 – the clock was cleaned, and then wound to run for just a week during that year. The first 3 clocks which require no lubrication, hence little cleaning, are kept running all the time.

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