Jim Thompson
Jim Thompson
By Jim Thompson
HCP columnist

Now the secret is out. If I was thinking of one person when I started this series, it was our next candidate up: John Harrison.

John Harrison lived from 1693-1776. He is at an interesting juncture in our chronology.

Isaac Newton was 52 when Harrison was born, and Gottfried Wilhelm (von) Leibniz was 47. George Washington was born when Harrison was 39. So, chronologically, he sits at important point in time – calculus has just been invented and the American Revolution is on the horizon.

Harrison needs the math of Newton and Leibenz, and Britain needs the work of Harrison to manage its colonies through the communications tool of the day – sailing ships.

Unless you have studied certain navigational subjects, you have likely never heard of John Harrison, but he is key to modern commerce (at least up to the point where we threw satellites up in the sky to aid in navigation).

Here is the practical problem Harrison spent his life solving. Up until Harrison’s time, it was fairly easy to determine a ship’s position north or south in the oceans (latitude). A skilled navigator shot the sun (daytime) or stars (nighttime) with the sextant and found a latitudinal solution.

Longitudinally, that is east or west, was another problem. Because the earth rotates, there is no fixed position in the heavens from which to take a reading. Smart folks figured out what the system might be to determine this, but they had no practical way to implement the solution.

This was indeed a serious problem. Ships kept running into land masses because they did not know where they were east and west.

The path to the solution was to have a highly accurate clock at a known longitudinal place then have another clock on board the ship set at the same time. Then from the ship, you could shoot the sun with your sextant at noon, look at the clock on board and calculate where you were, again, east and west, relative to the known clock on land. It is relatively simple math. If you had fairly accurate maps, you would then know where the next land mass was ahead of you. But you needed the clock.

The problem was no clocks had been invented with balanced pendulums that could withstand the rocking of a ship and still maintain accurate time. Essentially, all the clocks up to that time were of the grandfather clock style – a long swaying pendulum dependent on sitting on a solid surface in order to function accurately.

The problem of east-west determination was so important that British Parliament offered a prize of 20,000 English pounds to the person who could solve it (accounting for inflation and time, that is equivalent to U.S. $4.4 million today).

To make a long story short, Harrison started designing clocks to compete for this prize in 1730. Over time, Harrison made five clocks, labeled H1, H2, H3, H4 and H5. All these clocks are at the museum in Greenwich, England. I have visited them several times, for I find them fascinating.

H1 through H3 are fairly large devices; H4 was a breakthrough and looks like a very large gentleman’s pocket watch. H5 a further refinement. This was Harrison’s life’s work for which Parliament grudgingly paid him in small increments over time.

Today, we simply use GPS to determine our location. However, as recently as World War II, we were using methods similar to those of Harrison’s day. Bombers manufactured in the United States and ferried to Europe for the war were flown at night (so the stars could be seen and used to navigate). The machinery was removed from the top turret gunner position and the navigator’s assistant sat up there with a sextant and shot the stars to get the planes across the ocean. This is documented in the book “On Celestial Wings” by Edgar Whitcomb, former governor of Indiana.

Jim Thompson, formerly of Marshall, is a graduate of Hillsboro High School and the University of Cincinnati. He resides in Duluth, Ga. and is a columnist for The Highland County Press. He may be reached at jthompson@taii.com.