Compass: A Story of Exploration and Innovation

On opening any book, there can be surprises of both omission, and of commission, and this book was no exception. Finding where you are going has always been a prime use of a magnetic compass, but it is also very useful for finding where you are. A major surprise for me was the nature and complexity of compass errors that historically there have been. A compass is something that is there, and works, isn't it? Well ...... no! Alan Gurney concentrates, quite rightly in retrospect, in the use of the humble compass at sea. Errors at sea are quite costly, resulting in huge losses, both in terms of human life and the ships that carry the masters of the deck. There can be significant other consequences, sometimes directly financial, at other times a huge environmental impact. My perspective has always been the use of a compass on dry land, and attempting to find where I am, and how to get to where I want to be, oft-times across rugged terrain. Previous knowledge concerned the variation between true north and magnetic north, and the use of a compass in taking back-bearings. I learnt a significant amount from this historical account of the improvements in ship-born compasses. What was a surprise to me was how true north and magnetic north varies, both with respect to location and over time. Yes, I knew that the two directions are not the same. However, it was well described how setting a compass to compensate for the variations at, say, Falmouth, will be insufficient when sailing to Newfoundland. Gurney could have used more diagrams to illustrate the errors that exist with magnetic compasses. The errors themselves with dry-card compasses are neatly explained in an appendix, but diagrams would enhance the description. The means of compensating for the errors can be difficult to follow, and this is shown as some of the real improvements were only slowly recognised (the Flinders bar, and multi-needle compasses being cases in point). It is only now that I understand what a "binnacle" is - a case or box on the deck of a ship, generally mounted in front of the helmsman, in which navigational instruments are placed for easy and quick reference as well as to protect the delicate instruments. An overall explanation (as above) would have helped me, and no doubt others in their reading, rather than the word being used as if the reader has a working knowledge of the nautical term. However, Gurney explains well the need to have no iron in the construction of this navigational pulpit. He also gives a good guide to the difference between `soft iron' and `hard iron', and how this affects magnetic compasses. The emphasis in this volume is on the use of the compass up until the start of the 20th century. That was what Gurney set out to do, and in that he has written a good guide. The differences between wooden hulled vessels and their competitors and conquerors, the iron vessels, is well represented. It is obvious with hindsight, but iron vessels presented very diff

As a person with a special interest in boat navigation, this book caught my attention. I have other books on the subject, but I could recommend this one without reservation. It combines a history of the mariner's compass as developed in the west (with some comments on Chinese systems) with a great deal of technical information about compasses and compass use. It does all this in an easily-readable form. The information is spaced out with appropriate anecdotes so one is not hit with a lot of technology all at once. Readable and useful.

Compass takes us back to the day when compasses were not understood, performed poorly, broke (broke?), and often pointed many, many degrees from North. Yet it was all early mariners had. Alan tell the story of the development of the compass, particularly the marine compass, from the days of a magnitized piece of steel floating in a bowl of water to today's current marvel, with multiple magnets used to avoid sorts of errors like semicircular deviation and heeling error. Unfortunately, it is not equal to Dava Sobel's great book on Finding the Longitude. The information seems scarcer, and the writing is not quite as good. It is amazing to learn that almost 1,000 years had to pass before most if not all the errors of a compass were figured out and coorrected, Still highly recommnended If you navigate, you should have this book to learn the complexity of the compas in yout vehicle.

The compass is a fascinating instrument. So simple, but so critical to any traveler. Gurney starts by telling us about the compass disasters. Thousands of people have died by assuming the compass was a simple device, always true and easy to read. As any Boy Scout can tell you, the compass is almost always wrong. It is predictably wrong, but one needs to know the correction formula. Given this framework, Gurney organizes his tale upon two themes. First, how does the compass design facilitate easy readings and correct interpretation. Second, did governmental organizations contribute or impede good compass design. In the best light, bureaucracies have to balance the need for 'accuracy' against 'ease of use'. In the worst light, the story is simply one of greed and aristocratic pride. Gurney makes fun of magnetic charlatans and the bureaucrats they fool, but he could have done then settle for a good laugh. The book spends a chapter or two introducing the early evolution of navigational compasses, but doesn't really get interesting until Gurney's two themes come into focus. They emerge when the British Admiralty takes on the challenge of determining 'north' from an always shifting terrestrial magnetic field. Gurney does a good job bringing his cast of characters to life. There are funny tales about the Royal Society's first 'Museum of Natural History', which required one visit to 'apply' for a entry pass, a second visit to pick up the pass, and a third day trip to actually go inside. Another tales discusses a quack doctor's solution to impotence and fertility: 2 tons of magnets under a bed, a string quartet behind a curtain and a mattress filled with stallion hair. Astronomer Halley comes off looking like Star Trek's Captain Kirk. Lord Kevin's story is not so attractive.

No doubt the publisher's aim was to create another "Longitude", but I think "Compass" is even better. Gurney is very good at pen portraits of the many brilliant and eccentric characters who wander into his yarn. The sheer stubbornness with which extremely bright people defended their ideas, long after they were proved wrong or even dangerous, can give one pause. There's no shortage of people like that in our modern society. What gives the book its particular charm is that the story of the compass is one of advancing technology exposing ever-newer areas of ignorance. Before the first iron-hulled ship was built, who knew that pounding and riveting iron in a dockyard would magnetize the metal? Or that a compass on a metal-hulled ship would give different readings based on the direction the ship was facing?