Longitude is the dramatic human story of an epic scientific quest, and of John Harrison's forty-year obsession with building his perfect timekeeper, known today as the chronometer. Full of heroism and chicanery, brilliance and the absurd, it is also a fascinating brief history of astronomy, navigation, and clockmaking. Through Dava Sobel's consummate skill, Longitude will open a new window on our world for all who read it.
I would have enjoyed reading a bit more about the actual science, too. This is a pretty light and quick read--actually a bit too light for my liking. Sobel mentions various improvements that increased the accuracy of clocks, but I felt like most of the descriptions of the inner workings of clocks were a bit too vague to really give me an understanding of what goes on in there. For example, we learn that "the grasshopper escapement--the part that counted the heartbeats of the clock's pacemaker--took its name from the motion of its crisscrossed components. These kicked like the hind legs of a leaping insect, quietly and without the friction that had bedeviled existing escapement designs." This is all that's said about it, so it wasn't at all clear to me how exactly an escapement worked, and I would have liked to know.
Still, this was a fairly informative book, and probably worth reading, even if it's not anything outstanding. A lot of people will probably be grateful for the fact that Sobel doesn't go into more scientific detail.
Very well-written, never burdened by heavy citations or references, this popular account is a pleasurable read for everyone.
What is nice about this book is that there are no deviations from the story - no detailed and ponderous history of navigation since the Stone Age, no biographies beyond what is pertinent to the story. Just the facts, ma'am, just the facts.
Camelot & Vine
The book chronicles the history and political machinations surrounding the development of the first clocks suitable for maritime navigation.
The only negative was not about the story and the writing, but the edition I read. I read the illustrated version, and it was giant and difficult to hold while reading, some of the pictures also ruined the flow of the story in some places. If you are trying to decide which version to get, go with one of the smaller ones.
Moving on to the usual format of Good and Bad, the only real negative I would apply here is that it does at times seem a bit scattered, as if a good central idea was stretched a bit beyond its proper length. It just seems to meander rather randomly at times.
On the vast positive side, there are all sorts of delicious tidbits from history. So much so that it spurred me to write a blog entry just from the first few dozen pages. I'll reproduce it at the end as an illustration but in summary a very informative book filled with delightful anecdotes.
Tonight’s reading of Dava Sobel’s book ‘Longitude’ reminded me of one of my favorite great “difficulties” from history. Specifically, just how hard it has been throughout mankind’s existence to tell what exactly the time is. It is one of the most bedeviling of problems, since we live on a sphere and the motion of the sun and moon define the very concept of time for us. Unfortunately, twelve noon in New York looks exactly like twelve noon in New Delhi. The book’s topic is primarily that of determining longitude (obviously) but since this is so closely married to the more interesting problem of time-keeping, I felt it incumbent to tease out a few of the more interesting tidbits from tonight’s reading. It should be noted that I’ll only breeze over these points at the highest level. Anyone wanting to actually learn something should go read the book for themselves.
The book opens, and frames the problem of navigation with an ironic and grand story of misplaced wrath from 1707. A British naval officer is making his way home after a successful battle with a fleet of five ships on a very foggy evening. He is approached by a worried sailor who says his reckoning tells him that they are dangerously close to shore. The captain, offended by the affront, has the sailor hanged for mutiny. Minutes later, the entire fleet runs aground and the crews are almost entirely lost. With so few navigational aids, it was nearly impossible to be certain just how far east or west any ship might be. It all really boiled down to guesswork and even seasoned sailors were sometimes failures.
One early attempt at solving this problem comes from Galileo. He noted rightly that the moons of Jupiter eclipsed and reappeared with amazing regularity. He constructed a device called a Celatone, combining a helmet and telescope, to aid sailors in observing the various movements of the moons. This, combined with a detailed table of expected movements would provide the time assuming that it was dark… and a clear night… and Jupiter also happened to be on the right side of the planet to be seen. Needless to say, this didn’t quite catch on. Somewhat relatedly, many years later a Danish astronomer, Ole Roemer, observed that the schedule of Jovian eclipses was inaccurate by several minutes depending on the relative positions of Jupiter and Earth in the solar system. He was able to use these deviations to make an exceptionally good calculation of the speed of light, which was thought at the time to be transmitted instantaneously.
Lastly for tonight, and most abundantly oddball, we have the story of “Sympathy Powder” from 1687. Sir Kenelm Digby is said to have discovered a “miraculous” powder that had the power of healing people at a distance. The only down side was that it was a rather unpleasant sensation when put in use. Using this miraculous concoction, the idea was advanced that a dog should be put aboard ship with a festering wound. Each day at 12:00 local time, the powder would be applied to some personal effect belonging to the dog, thus causing it to yelp and alerting the ship’s crew to the real time back home. Issues with this approach abound, of course, but it is a little known fact that this exact method of timekeeping is widely in use today. It is precisely this form of chronology that Doctor’s use to know when appointments are to be kept, at least if my own personal experiences with their promptness are any indication.
The tracking and mapping of the heavens was in itself a monumental feat, as was the increasing understanding of the movement of stars and the moon and the ability to measure them accurately. So the struggle was between those who wanted the power and appeal of the celestial map against the less-divine mechanical solution. The latter won out because it proved itself time and again, and because a difference of only a few seconds a day could spell the difference between successful landfall and disaster. Sobel argues, without unfortunately elaborating much upon it, that the accurate measurement of longitude stimulated the expansion of British exploration and development of the British Empire.
I learned that the first fairly accurate measurement of the speed of light was made in 1676 by a Danish astronomer, Ole Roemer, based on calculations to do with the orbits of Jupiter moons! Amazing.
Latitude has always been simple to find, just take the angle from the horizon to the North Star. Determining one’s longitude was not so easy. Since the Earth rotates 360 degrees in 24 hours, the longitude of a location is the difference in time between noon at that location and noon at the reference meridian. Hence, an accurate method of determining time at these two locations is vital to determining longitude. The book Longitude, by Dava Sobel, tells of how this problem was solved by a persistent clock-maker in England in the eighteenth century.
The problem of fixing longitude is an old one. Without knowledge of the longitude, mariners navigated by dead-reckoning. A ship would sail along a coastline to a fixed parallel. Then turning seaward, it sailed along the parallel to the longitude of a distant port keeping track along the way by reckoning the distance traveled from the ships velocity and hour glasses. Sobel writes of Admiral Sir Clowdisley Shovell’s disastrous miscalculation on a foggy autumn night in 1707. Misjudging the ships location in fog, the Admiral’s five vessels sank and thousands of sailors died. Before longitude shoals of uncertainty and danger waited to sink the dreams of all who ventured beyond the horizon. The Longitude Act of 1714 offered a prize to anyone who solved the longitude problem.
A self-educated clock maker named John Harrison saw a precision time device as the solution to the longitude problem. Instead of going directly to the Board of Longitude, he presented his first clock, the H-1, to the Royal Society in hopes of winning crucial support of the device. The Society agreed to send the chronometer, as the clock came to be called, on an experiment with a departing ship. On the return voyage the ship’s captain made a miscalculation of position that Harrison corrected with his clock. The captain was thoroughly impressed with the performance of the device and encouraged the Royal Society to endorse it. Harrison however believed he could improve upon the design before going before the Board of Longitude for the prize offered in the Longitude Act. He received a loan for a member of the Royal Society and commenced work on the H-2.
As with all stories, an antagonist must introduce challenges for the main character. An antagonist would not be hard to find. Many established scientists staked their reputations on the astronomical solution to the longitude problem. It is Nevil Maskelyne, a villainous name if there ever was one, who emerges as the antagonist in this story. He was a contender for the Longitude prize, as well as a member of the Board of Longitude. Maskelyne is the type of scientist who uses political persuasion to advance acceptance for a hypothesis rather than data. Sobel tells one story of Maskelyne bringing several sailors to a board meeting to praise the success they had with Maskelyne’s lunar tables. Along with a sextant the lunar tables could fix longitude if the sky was clear. In Maskelyne’s mind, the chronometer could only play a supporting role to the astronomical attempt to fix longitude. As conflicting interests such as this typically do, this stalled the acceptance of any real solution for most of Harrison’s life.
One of the most influential supporters of the maritime chronometer was the circumnavigator Captain James T. Cook. He found a copy of Harrison’s fourth device, the H-4, to be most useful. According to Sobel, Cook entered into his journal of the 1772 expedition, “indeed our error (in Longitude) can never be great, so long as we have [the] watch.” Clearly Cook put a great deal of trust in the chronometer for his safe passage. Without a doubt Cook’s support helps to shift the paradigm. Ultimately it was the chronometer that took center stage and Maskelyne’s lunar tables played the supporting role. Cook and other mariners began using the watch exclusively and the lunar tables to maintain the accuracy of the watch.
Without the Harrison’s clocks much of the globe may have gone unexplored until much later in human history. The British Empire may not have ever established the Prime Meridian and each country would still arbitrarily choose it. As Paige Johnson of the Chemistry Department at The University of Tulsa said most eloquently “the chronometer was important shaped the world then and now it is GIS that is shaping the world.”