The Great Indian Arc of the Meridian, begun in 1800, was the longest measurement of the earth's surface ever to have been attempted. Its 1600 miles of inch perfect survey took nearly fifty years, cost more lives than most contemporary wars, and involved equations more complex than any in the pre-computer age. Hailed as 'one of the most stupendous works in the history of science', it was also one of the most perilous. Through hill and jungle, flood and fever, an intrepid band of surveyors carried the Arc from the southern tip of the Indian subcontinent up into the frozen wastes of the Himalayas. William Lambton, an endearing genius, had conceived the idea; George Everest, an impossible martinet, completed it. Both found the technical difficulties horrendous. With instruments weighing half a ton, their observations had often to be conducted from flimsy platforms ninety feet above the ground or from mountain peaks enveloped in blizzard. Malaria wiped out whole survey parties; tigers and scorpions also took their toll.

Yet the results were commensurate. The Great Arc made possible the mapping of the entire Indian subcontinent and the development of its roads, railways and telegraphs. India as we now know it was defined in the process. The Arc also resulted in the first accurate measurements of the Himalayas, an achievement which was acknowledged by the naming of the world's highest mountain in honour of Everest. More important still, by producing new values for the curvature of the earth's surface, the Arc significantly advanced our knowledge of the exact shape of our planet.

"More extraordinary than any fiction."
CHARLOTTE CORY, MAIL ON SUNDAY

"A triumph."
ANDREW TAYLOR, LITERARY REVIEW

"This wonderful book – surely Keay's most compelling, and one of the most remarkable works of non-fiction to be published this year – is a fitting monument not just to Everest but also to the Great Arc itself."
WILLIAM DALRYMPLE, SUNDAY TIMES

OS Explorer is the Ordnance Survey's most detailed map and is recommended for anyone enjoying outdoor activities like walking, horse riding and off-road cycling. The OS Explorer range now includes a digital version of the paper map, accessed through the OS smartphone app, OS Maps. Providing complete GB coverage the series details essential information such as youth hostels, pubs and visitor information as well as rights of way, permissive paths and bridleways.

OS Explorer is the Ordnance Survey's most detailed map and is recommended for anyone enjoying outdoor activities such as walking, horse riding and off-road cycling. The series provides complete GB coverage and can now be used in all weathers thanks to OS Explorer - Active, a tough, versatile version of OS Explorer. The OS Explorer Active range now includes a digital version of the paper map, accessed through the OS smartphone app, OS Maps.

OS Explorer is the Ordnance Survey's most detailed map and is recommended for anyone enjoying outdoor activities such as walking, horse riding and off-road cycling. The series provides complete GB coverage and can now be used in all weathers thanks to OS Explorer - Active, a tough, versatile version of OS Explorer. The OS Explorer Active range now includes a digital version of the paper map, accessed through the OS smartphone app, OS Maps.

OS Explorer is the Ordnance Survey's most detailed map and is recommended for anyone enjoying outdoor activities such as walking, horse riding and off-road cycling. The series provides complete GB coverage and can now be used in all weathers thanks to OS Explorer - Active, a tough, versatile version of OS Explorer. The OS Explorer Active range now includes a digital version of the paper map, accessed through the OS smartphone app, OS Maps.

OS Explorer is the Ordnance Survey's most detailed map and is recommended for anyone enjoying outdoor activities such as walking, horse riding and off-road cycling. The series provides complete GB coverage and can now be used in all weathers thanks to OS Explorer - Active, a tough, versatile version of OS Explorer. The OS Explorer Active range now includes a digital version of the paper map, accessed through the OS smartphone app, OS Maps.

OS Explorer is the Ordnance Survey's most detailed map and is recommended for anyone enjoying outdoor activities such as walking, horse riding and off-road cycling. The series provides complete GB coverage and can now be used in all weathers thanks to OS Explorer - Active, a tough, versatile version of OS Explorer. The OS Explorer Active range now includes a digital version of the paper map, accessed through the OS smartphone app, OS Maps.

OS Explorer is the Ordnance Survey's most detailed map and is recommended for anyone enjoying outdoor activities such as walking, horse riding and off-road cycling. The series provides complete GB coverage and can now be used in all weathers thanks to OS Explorer - Active, a tough, versatile version of OS Explorer. The OS Explorer Active range now includes a digital version of the paper map, accessed through the OS smartphone app, OS Maps.

OS Explorer is the Ordnance Survey's most detailed map and is recommended for anyone enjoying outdoor activities such as walking, horse riding and off-road cycling. The series provides complete GB coverage and can now be used in all weathers thanks to OS Explorer - Active, a tough, versatile version of OS Explorer. The OS Explorer Active range now includes a digital version of the paper map, accessed through the OS smartphone app, OS Maps.

OS Explorer is the Ordnance Survey's most detailed map and is recommended for anyone enjoying outdoor activities such as walking, horse riding and off-road cycling. The series provides complete GB coverage and can now be used in all weathers thanks to OS Explorer - Active, a tough, versatile version of OS Explorer. The OS Explorer Active range now includes a digital version of the paper map, accessed through the OS smartphone app, OS Maps.

OS Explorer is the Ordnance Survey's most detailed map and is recommended for anyone enjoying outdoor activities such as walking, horse riding and off-road cycling. The series provides complete GB coverage and can now be used in all weathers thanks to OS Explorer - Active, a tough, versatile version of OS Explorer. The OS Explorer Active range now includes a digital version of the paper map, accessed through the OS smartphone app, OS Maps.

OS Explorer is the Ordnance Survey's most detailed map and is recommended for anyone enjoying outdoor activities such as walking, horse riding and off-road cycling. The series provides complete GB coverage and can now be used in all weathers thanks to OS Explorer - Active, a tough, versatile version of OS Explorer. The OS Explorer Active range now includes a digital version of the paper map, accessed through the OS smartphone app, OS Maps.

OS Explorer is the Ordnance Survey's most detailed map and is recommended for anyone enjoying outdoor activities such as walking, horse riding and off-road cycling. The series provides complete GB coverage and can now be used in all weathers thanks to OS Explorer - Active, a tough, versatile version of OS Explorer. The OS Explorer Active range now includes a digital version of the paper map, accessed through the OS smartphone app, OS Maps.

OS Explorer is the Ordnance Survey's most detailed map and is recommended for anyone enjoying outdoor activities such as walking, horse riding and off-road cycling. The series provides complete GB coverage and can now be used in all weathers thanks to OS Explorer - Active, a tough, versatile version of OS Explorer. The OS Explorer Active range now includes a digital version of the paper map, accessed through the OS smartphone app, OS Maps.

OS Explorer is the Ordnance Survey's most detailed map and is recommended for anyone enjoying outdoor activities such as walking, horse riding and off-road cycling. The series provides complete GB coverage and can now be used in all weathers thanks to OS Explorer - Active, a tough, versatile version of OS Explorer. The OS Explorer Active range now includes a digital version of the paper map, accessed through the OS smartphone app, OS Maps.

OS Explorer is the Ordnance Survey's most detailed map and is recommended for anyone enjoying outdoor activities such as walking, horse riding and off-road cycling. The series provides complete GB coverage and can now be used in all weathers thanks to OS Explorer - Active, a tough, versatile version of OS Explorer. The OS Explorer Active range now includes a digital version of the paper map, accessed through the OS smartphone app, OS Maps.

OS Explorer is the Ordnance Survey's most detailed map and is recommended for anyone enjoying outdoor activities such as walking, horse riding and off-road cycling. The series provides complete GB coverage and can now be used in all weathers thanks to OS Explorer - Active, a tough, versatile version of OS Explorer. The OS Explorer Active range now includes a digital version of the paper map, accessed through the OS smartphone app, OS Maps.

OS Explorer is the Ordnance Survey's most detailed map and is recommended for anyone enjoying outdoor activities such as walking, horse riding and off-road cycling. The series provides complete GB coverage and can now be used in all weathers thanks to OS Explorer - Active, a tough, versatile version of OS Explorer. The OS Explorer Active range now includes a digital version of the paper map, accessed through the OS smartphone app, OS Maps.

OS Explorer is the Ordnance Survey's most detailed map and is recommended for anyone enjoying outdoor activities such as walking, horse riding and off-road cycling. The series provides complete GB coverage and can now be used in all weathers thanks to OS Explorer - Active, a tough, versatile version of OS Explorer. The OS Explorer Active range now includes a digital version of the paper map, accessed through the OS smartphone app, OS Maps.

OS Explorer is the Ordnance Survey's most detailed map and is recommended for anyone enjoying outdoor activities such as walking, horse riding and off-road cycling. The series provides complete GB coverage and can now be used in all weathers thanks to OS Explorer - Active, a tough, versatile version of OS Explorer. The OS Explorer Active range now includes a digital version of the paper map, accessed through the OS smartphone app, OS Maps.

The young, volcanic, Galapagos Archipelago is made up of over 130 islands and islets, although only five are actually inhabited. A province of Ecuador, they are located on the Equator, about 1,000 km (about 600 miles) to the west of South American mainland. Aside from their natural beauty, and the opportunities for exploration by sea, the Galapagos Islands are intimately associated with scientific research. While this may have begun with Charles Darwin's brief visit in 1835, today the emphasis is on conservation research, and the islands and surrounding marine reserve form a UNESCO Natural World Heritage Site.The Galapagos Islands Explorer is a fold-out visitor's map (scale 1 : 400 000), that measures approximately 100 x 69 cm (W x H) when unfolded. It also has sections on human history, conservation, National Park Rules, the various island names (Ecuadorian and English), a timeline, and biographies of the significant people in Galapagos history. It will complement a trip to the islands, and help you make the most of your time there.Mapping has come a long way since the islands first appeared on Gerardus Mercator's map in 1569, and the Galapagos Islands Explorer is the perfect companion for a visit to the archipelago. As well as the map itself, the Explorer gives a general introduction to the geology, climate, and geography of the islands, plus background background information on the flora and fauna you can expect to see - from Galapagos cotton to the famous iguanas and giant tortoises. There is concise and practical information on each of the main islands as well as the most popular dive sites.

OS Explorer is the Ordnance Survey's most detailed map and is recommended for anyone enjoying outdoor activities like walking, horse riding and off-road cycling. The OS Explorer range now includes a digital version of the paper map, accessed through the OS smartphone app, OS Maps. Providing complete GB coverage the series details essential information such as youth hostels, pubs and visitor information as well as rights of way, permissive paths and bridleways.

OS Explorer is the Ordnance Survey's most detailed map and is recommended for anyone enjoying outdoor activities such as walking, horse riding and off-road cycling. The series provides complete GB coverage and can now be used in all weathers thanks to OS Explorer - Active, a tough, versatile version of OS Explorer. The OS Explorer Active range now includes a digital version of the paper map, accessed through the OS smartphone app, OS Maps.

OS Explorer is the Ordnance Survey's most detailed map and is recommended for anyone enjoying outdoor activities like walking, horse riding and off-road cycling. The OS Explorer range now includes a digital version of the paper map, accessed through the OS smartphone app, OS Maps. Providing complete GB coverage the series details essential information such as youth hostels, pubs and visitor information as well as rights of way, permissive paths and bridleways.