PASTIME


engineering breakthroughs and the development by Harrison himself and by other watchmakers of precision movements on a much smaller scale than had previously been thought possible.


The H4, which measures 5.2 inches in diameter, was trialled in 1761. On arrival in Jamaica following a voyage from England, the H4 was four minutes slow, an error in longitude of 1.25 minutes or about one nautical mile. Despite this, the Board of Longitude refused to pay the full £20,000 to Harrison and demanded another trial. Harrison by this time, was working on the next iteration – the H5. By the time of his death in 1776, the Board of Longitude had finally acknowledged Harrison. Captain James Cook used copies of his H4 on his historic voyages to the southern Pacific.


Chris goes on: “Accurate clocks are one of the things that made


Chris concludes: “As a business we also find John Harrison a real stimulus to our work. He showed a combination of determination, grit, fortitude and perseverance plus a touch of genius –he is probably the finest watchmaker that we have ever had and his legacy goes on today.”


Britain great in the 18th and 19th centuries. Before Harrison’s invention crossing oceans was not easy – sailors just could not plot with any accuracy.” Christopher Ward is marking the 250th anniversary of the H4 with a series of three automatic watches, the C9 Harrisons. Each has a quintessentially English appearance, and complications that nod to Harrison’s own timepieces – two time zone settings prevalent among them.


Chris concludes: “As a business we also find John Harrison a real


stimulus to our work. He showed a combination of determination, grit, fortitude and perseverance plus a touch of genius – he is probably the finest watchmaker that we have ever had and his legacy goes on today.”


For the full story on John Harrison’s amazing journey of invention, Chris recommends Dava Sobel’s Longitude, published by Fourth Estate, and the ITV DVD of the book, first broadcast in 2000.


See pages 46 to 50 for the full range of Christopher Ward watches.


Longitude and Latitude


What’s the difference between longitude and latitude?


Lines of latitude run in parallel to each other, rounding the globe to the north and to the south from the mid-point Equator, which is at 0º latitude. They stay parallel to each other in concentric rings of decreasing size. Key lines of latitude in addition to the Equator are the Tropic of Cancer and the Tropic of Capricorn. These tropics mark the high points of the sun in summer in the northern and southern hemispheres, respectively.


Lines of longitude, on the other hand, straddle the globe in circles of the same size, that converge north and south at the Poles. The 0º longitude line, the Prime Meridian, runs through Greenwich in London – hence Greenwich Mean Time. The Prime Meridian has, however, moved to different locations over time, reflecting political and scientific power at any time. The Canary Islands, Paris, St Petersburg, Rome and Jerusalem have


all been named as home to 0º longitude, among others, over the past 2,000 or more years


What is the longitude problem? The nub of the problem was for ships’ navigation. Latitude is fixed, and if you can see the sun, experience the length of the day, and read the stars at night you can calculate your position north to south. Sailors have been able to do this for millennia.


But the globe turns every 24 hours, so moving across the globe east or west is based on changing time and not a fixed position. As the globe turns 360º in 24 hours, each hour’s journey is equivalent to 15º of longitude, which is one hour difference in time. To calculate your ship’s distance travelled you need to know the time at your port of departure as well as the time on board. And to do this, you need to have clocks that work with absolute precision.


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