The Great Arc Page 6
Henry, however, was much more confident; for Webb too had submitted observations of a peak which, taken from four different stations on the Nepal border, gave a height of 26,862 feet. Moreover Webb had a name for his peak; he understood that it was called Dhaulagiri, or ‘The White Mountain’. So it still is; and within fifty feet, Webb’s height is indeed the height now given to Dhaulagiri, the world’s seventh highest mountain. But luck as much as science had produced the figure; and Henry Colebrooke then made matters worse by dismissing it as an underestimate; he reckoned Webb’s observations gave ‘more than 28,000 feet above the level of the sea’. The conclusion of Colebrooke’s paper was therefore no surprise.
I consider the evidence to be now sufficient to authorize an unreserved declaration of the opinion, that the Himalaya is the loftiest range of Alpine mountains which has yet been noticed, its most elevated peaks greatly exceeding the highest of the Andes.
First published in the journal of his Bengal Asiatic Society and then widely reported in Europe, Colebrooke’s findings caused a minor sensation. But they came up against a certain indifference to all things Indian and were not readily accepted. Armchair scholars, inured to absurd claims from the land of rope-tricks and reincarnation, pooh-poohed these tall tales from the hills. Even recognised authorities with some experience of the Himalayas were not readily convinced. Henry Colebrooke seemed to have overstated his case, to have protested too much. High as they undoubtedly were, the Himalayas were too inaccessible and mountain surveying too approximate to justify his sweeping conclusions.
The most disparaging notice came from the most influential publication. In the Quarterly Review, a magisterial journal which until the foundation of London’s Royal Geographical Society monitored the course of discovery, an anonymous but highly competent reviewer found Colebrooke’s paper ‘most curious’. He had no complaint about Colebrooke’s methods or his mathematics but, dealing in turn with each of his cited examples, he demolished them one by one. Crawford’s Nepal observations were ‘of very little value’ because his bearings, distances and triangles were unknown. Robert Colebrooke never got nearer than ninety miles to any of his measured peaks, nor did Webb to Dhaulagiri, and nor had Henry Colebrooke at Purnia. Even assuming that the supposed distances were nevertheless correct, the observed angles of elevation, typically about one to three degrees above the horizontal, were too small for confidence. For every error of one second of one minute of a degree (so 1/360th of a degree) in either the instrument or the observation, fifty feet would be added to or subtracted from the supposed height.
And then there was the problem of refraction. The table of allowances which Robert Colebrooke had used was deduced from astronomical observations. It was never intended for terrestrial observations at such low angles over such long distances. The Quarterly Review’s contributor went into this problem in some detail. Peering out across the English Channel the people of Dover could sometimes see the houses of Calais standing proud of the sea, and at other times, when the atmosphere was equally clear, they could not see them at all. Whale fishers moored off Greenland had noticed the same phenomenon, with snow cliffs appearing and disappearing above the horizon according to the state of the weather and the position of the ice. The whalers called it ‘ice-blink’ and reckoned that objects thirty miles ‘beyond the limit of direct vision’ could yet be clearly seen when conditions were favourable. Temperature, humidity and even the time of the day all seemed to affect the amount of refraction, and in one case it had been found to increase angles of observation by over four degrees. Given that in India the difference of temperature between points of observation in the plains and the ice-encrusted pinnacles protruding above the clouds might be a good 100 degrees Fahrenheit, the properties of refraction could only be guessed at.
In short, Colebrooke’s advocacy was fatally flawed. His facts were ‘insufficient’, his data ‘incorrect’, his conclusions ‘hasty’. ‘On every consideration therefore,’ intoned the Review, ‘we conceive that we are borne out in concluding that the height of the Himalaya mountains has not yet been determined with sufficient accuracy to assert their superiority over the Cordilleras of the Andes.’
Colebrooke’s response, if any, is not known. But already Webb and a younger generation of surveyors were addressing these criticisms with fierce determination. Their professional competence had been questioned and the honour of their service was at stake. New measurements were being attempted from much more favourable locations, and new proofs would soon be adduced. For by the time that the 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 the Himalayas. 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
Crossing 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 baronial chief. Clearly in India as elsewhere the planting of flags had territorial connotations. Lambton’s willingness to adopt whatever flag was locally acceptable made little difference. Eventually the Survey would opt for other sighting marks of a less contentious nature, like a sturdy sapling or a basket atop a pole.
Lambton’s men beat a speedy retreat from Narnicul only to be denied again at the next droog. This time the reason given was ‘that, as it commanded a view of [the poligar’s] habitation, his women might be exposed to view’. Such accusations of voyeurism would be another recurrent problem. Elevations invariably commanded the privacy of someone’s home, and it was soon common knowledge that the survey’s instruments had the ability to magnify distant objects, persons or parts of persons to very intimate effect. Worse still, these monstrous machines not only magnified the object but inverted it. Respectable wives and daughters going about their domestic duties were being upended by perfect strangers with lascivious intent; cherished temples were being casually overturned; and if a well ran dry, it must be because the same troublemakers had tipped it upside down. Nor was it much good these injured people directing Lambton’s men to some less objectionable vantage point well out of harm’s and harems’ way. ‘I must place myself on such hills as will descry preceding and succeeding points,’ expostulated one of his assistants, ‘and these in a hilly tract like this are generally the highest and almost everywhere the stronghold of a poligar.’
The local people were unimpressed; and as for explanations about making maps or measuring the earth, what did these strangers take them for? Maps were made by pacing the roads with pen and paper, not by sitting on hills and tinkering with machines. Besides, everyone knew that if you needed to travel somewhere you found a man who knew the way. Why, even the surveyors were always asking for directions.
Coincidentally, a member of the Madras government’s finance committee was reported to have made exactly the same point. ‘If any traveller wishes to proceed to Seringapatam [Srirangapatnam], he need only say so to his head palanquin bearer, and he vouched that he would find his way to that place without having recourse to Lambton’s map.’ The speaker was objecting to the heavy expenditure involved in a trigonometrical survey. Luckily others, including the Governor of Madras, considered the enterprise ‘a great national undertaking’. Admittedly the Governor was one of those who were slightly mystified by its geodetic significance; but scientific opinion was evidently impressed and, if the reputation for enlightened government of British India, and Madras in particular, might thereby be advanced, so be it.
Lambton was nevertheless expected to operate on what Robert Colebrooke, with his flotilla of boats and his circus of marquees, elephants and camels, would have considered a wretched shoestring. ‘Tents:’ ran Lambton’s list of sanctioned equipment, ‘1 Marquee, 2 Private, 1 Necessary, 1 Observatory.’ The ‘Marquee’ was both his office and living quarters; the two ‘Private’ were needed for storing baggage; the ‘Necessary’ was for his commode – very necessary given the incidence of dysentery; and the ‘Observatory’ was for his Great Theodolite. There were no tents at all for his men, who presumably sheltered beneath whatever they could rig up by way of a canopy.
Precisely how many men were attached to the Survey in its early days is uncertain. For carriage purposes Lambton was initially allowed bullock carts and porters sufficient for the tents and instruments plus two messengers, eight lascars, two water-carriers, a carpenter, a blacksmith and an interpreter. This complement, perhaps forty in total, would soon double. It was found, for instance, that moving a delicate instrument like the Great Theodolite by bullock cart was not good for it. The badly rutted roads caused constant vibration and seldom went anywhere near the pre-selected heights. Infinitely preferable were porters, who were trained to treat their load with the care it deserved. But for half a ton of machinery that meant having at least two relays, each of twelve men, dedicated solely to this job. A military escort was also found necessary, partly to overawe hostility as in the case of the poligars, and partly to prevent the theft of instruments whose brass fittings were easily mistaken for gold. The escort comprised the Indian equivalent of a sergeant, two corporals and two dozen privates, another twenty-seven mouths to feed.
Additionally many of these men – including, it seems, Lambton himself – might summon their families whenever the Survey made a prolonged stop, usually to measure a base-line. If one of Lambton’s two European assistants happened also to be present along with his own train of dependants, the concourse would be considerable. To men who spent most of their working lives humping loads up hills in the back of beyond, such tented gatherings in the open country were a welcome relief. They were both the social and professional climax of the surveyor’s year. Discipline could be more relaxed; base-line romances became a cliché of Survey life.
In 1804, having carried his triangles from Madras to Bangalore, Lambton pushed on to the west, leaving the measurement of his second base-line to his senior assistant, Lieutenant John Warren. Warren, a fellow-officer in the 33rd Foot, had transferred from Mackenzie’s topographical survey much to the latter’s regret. His easy-going charm cemented a lasting friendship with Lambton and, as another self-taught astronomer and mathematician, he enjoyed his superior’s complete confidence. Nor did he disappoint. The Bangalore base-line took forty-nine days to measure and provided triumphant vindication of Lambton’s meticulous methods. For it was found that the measurement of the base by chain along the ground differed from that calculated by the triangulation brought up from the Madras base-line, all of two hundred miles away, by just 3.7 inches in the total length of 7.19 miles. Whatever critics thought about the need for Lambton’s Survey, they could hardly be unimpressed by its extraordinary accuracy.
Happily, troublesome poligars were not found west of Bangalore. Across the Karnataka plateau, the going was easier and admitted of the largest triangle yet measured. It is a good fifty miles from Savendroog on the outskirts of Bangalore to Mullapunnaletta, a hill just west of what Lambton calls ‘the Great Statue’ at Sravana Belgola (a prominent Jain figure, bolt upright and stark naked, which is still the world’s largest monolithic sculpture). Yet in the excellent visibility the hilltop statue and then the survey flag were clearly sighted through the theodolite’s telescope, and this line duly formed one side of a giant triangle.
Under such conditions a trigonometrical survey could move much faster than its topographical counterpart. Mackenzie, whose relations with Lambton were more correct than warm, was urging forward the men of his Mysore Survey so as to reach the west coast first. The breadth of the peninsula was ‘much wanted’, as Mackenzie put it, and he was ‘very desirous of having this closed first by our Survey for early communication to England’. Specifically ‘it would give me great pleasure if [reaching the coast] was effected before Captain Lambton’. In fact, his surveyor who was nearest to the coast was to make a dash for it as soon as Lambton hove into sight; but ‘do not,’ Mackenzie underlined, ‘mention this to anyone whatever as I confide in yourself alone.’
Mackenzie’s men had been in the field two years longer than Lambton’s. It seemed only right that their Mysore Survey should have the honour of crossing Mysore first and so completing the first trans-peninsular triangulation. But pushing their perambulators, pausing every few miles to plot relevant features on their plane-tables, and operating with inferior instruments and much shorter triangles, they were at a serious disadvantage. In long strides like that from Bangalore to Sravana Belgola, Lambton swept past them unnoticed.
There is no evidence that he was responding to Mackenzie’s challenge, or was even aware of it. He continued to insist on observing each of his angles on at least four separate occasions. And each time he continued to insist on the theodoli
te being reversed at least once: from two readings taken on opposite sides of the three-foot circle, or calibrated dial, he could allow for any inaccuracy in the original calibration of its degrees, minutes and seconds (so small that they had to be read with a microscope); such errors could then be rectified by taking the mean of the two sets of observations. Indeed it seems probable that, but for that ‘old accident’ with the Canadian eclipse, he would also have insisted on separate readings of every angle with first the left eye, then the right.
Likewise he always insisted on taking measurements from all three angles of every triangle. Mathematically, if two angles were known and due allowance made for spherical excess, the third could be calculated. But Lambton strongly remonstrated against any such short-cut. Every angle must be measured. It was the only way to detect errors and it was the only way to discover those variations in the spherical excess so vital to geodesy. Taking the third angle usually meant another long march, the scaling of another scorching droog, and then waiting days for perfect visibility – all in pursuit of a value already known to within the smallest fraction of a second of a minute of a degree. But Lambton would not be hurried; and the scientific establishment, if not the government, approved. As the eminent Scottish mathematician and geologist John Playfair would quaintly put it, ‘Lambton has no appearance of a person who would save labour at the expense of accuracy.’
To complete the longitudinal arc across the peninsula from coast to coast, it remained to carry Lambton’s triangles up to the crest of the Western Ghats and down to the sea. The Ghats, a formidable range which runs the entire length of India’s west coast, represented the Survey’s first mountain challenge. The dense forests and choked ravines of the Ghats were even more impenetrable than the Kistna-Godavari jungles which would so impress George Everest; and their moist malarial climate, at its worst in the post-monsoon period when Lambton made his final push, was deemed even more lethal. In a note ‘Regarding Diseases of the Malabar Woods’ a military engineer who had lately been based in the region warned of its extreme ‘unhealthfulness’ and appended some preventative tips which Lambton might have done well to disregard. They were: