Free The Great Arc by John Keay

Quarterly Review ’s findings had circulated in India, that long-awaited access to a section of the Himalayan glacis had been opened up. Courtesy of the 1814–15 Gurkha, or Anglo – Nepali, War, a slice of the Himalayas between Dehra Dun and the present Nepal frontier had at last been detached from Nepali sovereignty. The highest peaks in the central Himalayas remained shrouded in a haze of Nepali xenophobia, but at their western extremity, in the newly acquired states of Kumaon and Garhwal, there lay lesser giants which, if convincingly measured, could establish the primacy of the Himalayas.
    And then there was Lambton. In a sense the exacting standards which he was setting in the extreme south lent weight to criticisms of the rough-and-ready methods and the hit-and-hope calculations adopted by his Himalayan contemporaries in the north. If Lambton could satisfy the demands of European scientists, indeed exceed them, then those same scientists felt entitled to expect equivalent standards of accuracy in respect of claims for the Himalayas.
    At a time when the height of Mont Blanc was still unknown to within a thousand feet, this was asking a lot. But there was good news as well as bad. Lambton’s Great Arc of the Meridian, having been carried down to the tip of the peninsula, was now heading north. A thousand miles of hill, forest and plain, much of it not British territory and some of it deemed quite impossible to triangulate, still separated the Arc from theHimalayas. Nor was there any plan to extend it that far. But already Lambton was demonstrating that in the delicious precision of his triangulated distances and heights lay the key to measuring mountains.

FOUR

Droog Dependent
    C rossing southern India by rail one passes isolated hills which, seemingly dumped at random, are often composed of colossal boulders. They look geologically misplaced, like trophies gathered from afar by some forgotten race of megalithic hoarders. To the upland peninsula’s otherwise monotonous succession of wide fields and parched pastures they lend an outlandishness which can be disconcerting. Roused by a vague sense of unease, you look around for giants.
    In Karnataka such hills are known as droogs , and many once featured as military redoubts during the Anglo – Mysore wars. Similar fangs of rock in the low-lying plains of Tamil Nadu poke through the lush carpet of paddy fields west and south of Madras. The most impressive, like those at Jinji and Trichy (Tiruchirapalli), host impregnable forts and are crowned with tiny windswept temples.
    Bangalore-bound from Madras on the Brindavan Express, it occurred to me that a surveyor, invited to design the perfect terrain for triangulation, might well have come up with a landscape model very like the countryside of northern Tamil Nadu or Karnataka. Large, fairly level plains dotted with droogs at convenient distances were just what the triangulator ordered. Enjoying a fine, clear climate, not over-endowed with forest, not too densely populated, and yet affording ample supplies, this slice of peninsular India was the ideal place to field-test a trigonometrical survey.
    After twenty years’ experience in less favoured districts, William Lambton would probably have agreed. But he had not seen it that way in 1803. As he began constructing his first triangles west from Madras to Bangalore and on across the width of the peninsula, he anticipated only difficulties. Droogs , for instance, were not necessarily where he wanted them, and when they were, they were not always available. Barely a hundred miles inland from Madras he was obliged to realign the whole northern edge of his chain of triangles. A party sent on ahead to erect a flag at a place called Narnicul had found the desired droog defended by ‘men with matchlocks, swords and daggers’. They ridiculed the written instructions of the nearest British official and insisted that they held the place in the name of their local ‘poligar’ or