When science author Dava Sobel attended an obscure symposium in 1995 that was focused on the history of longitude determination she had no idea that her resulting book would capture the imagination of millions, spark a minor revolution in science writing and almost single-handedly ruin the antique chronometer market for collectors everywhere.
Sobel's book, 'Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time' is a true minor classic and stands as one of the best pieces of popular science literature and history ever written. High praise, eh? Well, her work deserves it!
Precise ocean navigation was a problem that vexed seafarers for hundreds of years. Once Christopher Columbus sailed westward over the horizon and discovered the rich (and exploitable) Americas the rush was on. The English, Spanish, Portuguese, French and Dutch soon found themselves in a mad race to plant the flag on these new continents and extract as much wealth as possible. The riches of the New World were limitless - timber and fur at first, mixed with some precious metals. Once agriculture was established, sugar cane, tobacco and eventually cotton became the huge exports that drove large scale agricultural commercialization, and very quickly drove the need for cheap labor - African slaves.
The situation got even worse when Magellan rounded the tip of South America and proved that the Atlantic and Pacific oceans were linked. Suddenly the entire Pacific Ocean was opened to sea-borne trade from the west. The Spanish in particular heavily exploited the trans-Pacific trade routes, moving the wealth of the orient - spices, plants, gems and precious metals - from the Philippines eastward across the Pacific to New World outposts. In major Spanish settlements on the Pacific side of the Americas like Panama City this Far East treasure was mixed with the riches of the New World, hauled overland to bustling cities like Portobello in Panama and loaded onto waiting galleons for movement on to Spain.
The New World had become a limitless warehouse of raw material that drove the exploding economies of Western Europe.
Yet, all this movement of raw material from the New World to the Old was accomplished using imprecise and error-prone methods of navigation.
Determining latitude (distance north or south of the equator) was fairly easy, and just about every seafaring culture figured it out early in their history. Latitude determination is as easy as measuring the angle of the pole star above the horizon, and that angular distance is your latitude.
Longitude, however, was an entirely different matter. Longitude determination is really the measurement of time - the time difference in hours, minutes and seconds between your current location and a known reference location. Conceptually it is pretty simple - determine precisely when local noon occurs at your location and compare that time with local time at a reference location. That time difference, expressed in degrees, minutes and seconds, is your longitude. The mathematics are really quite simple and easily grasped by any marginally educated ship captain or sailing master.
(Today we refer to that reference location as the Prime Meridian, or the zero line of longitude. By international agreement the Prime Meridian runs through the Royal Observatory at Greenwich, England. All longitudinal measurements today are based off of this Prime Meridian. Since the British Government also installed reference clocks in the Royal Observatory this is the genesis of the term 'Greenwich Mean Time' or GMT. But I'm getting ahead of the story.)
Countries, navies, ship owners and ship captains were losing far too many vessels, far too much cargo and far too many souls to bad navigation. By the early 1700s the 'longitude problem' had become one of the critical issues of the time. It occupied the thoughts of kings, admirals, sea captains and scientific thinkers across Europe.
One thing stood in the way of the longitude - accurate time keeping. To accurately determine longitude you need accurate clocks - clocks that can keep time to within a few seconds while carried aboard ships that are pitching and rolling in the open sea. By the early 18th Century it was thought that such clocks were beyond the capabilities of man. Some of the best minds in Europe were so convinced of this that they investigated other methods, some quite goofy: moor ships at pre-determined intervals across the Atlantic and have them all fire a cannon at a pre-determined time of day, map the lines of magnetic declination (deviation) and develop charts that relate declination to longitude, and my personal favorite, the 'powder of sympathy'. From Wikipedia:
"The powder (of sympathy) was also applied to solve the longitude problem in the suggestion of an anonymous pamphlet of 1687 entitled "Curious Enquiries." The pamphlet theorized that a wounded dog could be put aboard a ship, with the animal's discarded bandage left in the trust of a timekeeper on shore, who would then dip the bandage into the powder at a predetermined time and cause the creature to yelp, thus giving the captain of the ship an accurate knowledge of the time"
OK, the howling dog trick didn't work, but other methods actually came quite close. One technique called the lunar distance method actually worked, but was difficult to execute on the deck of a pitching ship and required a good bit of complex math. It may have worked, but it wasn't really practical.
In one of the first examples of applied research the British Parliament established a competition known as the 'Longitude Prize'. Anyone who came up with an accurate and easy to execute method for determining longitude at sea could claim a quite substantial prize and the accolades of scientists and sailors around the world.
Into this breach stepped a young self-taught clock maker and wood worker named John Harrison. A remarkable natural talent combined with keen intelligence led him, over the course of almost 30 years, to develop a series of clocks that held remarkable accuracy while at sea. His culminating achievement, the H-4 (Harrison Number 4) is the clock that ultimately won him the Longitude Prize and served as the pattern for all mechanical marine chronometers that followed.
Ms. Sobel's fine book details the story of John Harrison's development of the marine chronometer and overlays it with all of the political intrigue, scientific backstabbing and, ultimately, royal intervention that swirled around Harrison's work. Harrison's winning of the Longitude Prize was not a foregone conclusion, and he had to fight for recognition and prove and re-prove his invention time and again. Eventually he triumphed, and the concept of time-based longitude determination remained the standard until the advent of GPS late in the 20th Century.
'Longitude: The Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time' is a marvelous little work - well researched, engagingly written and a joy to read. I've read my copy at least three times since first buying it back in 1998. In fact, I've given away four or more copies to friends and relatives who expressed an interest in the topic. When I decided to make 'Longitude' this month's book selection I went hunting for my old copy. I couldn't find it, and I guess I must have loaned it out or given it away. I immediately ordered another copy from Amazon, but this time I ordered the illustrated edition. I must say that this newer edition is even better than the original. All the text of Sobel's original work is there, but the story is enhanced by a large number of very well chosen and annotated illustrations and photographs. It makes a great story better!