The Great Arc

by John Keay

  Under something of a cloud, therefore, in 1837 the primary triangulation was at last carried south to Sironj. It was not a place which Everest recalled with affection. Back in 1824–5, the supposed insubordination of Olliver, the ‘uncouth’ language of Rossenrode, and the volubility of Rossenrode’s horse had here driven him to the brink of insanity. Nor did he now have reason to revise his opinion of the place; for what should have been a major triumph with the completion of the Great Arc from one end of India to the other was marred by a fatal revelation. The base-line at Sironj as calculated by the triangulation carried down from the base in the Dun was found to differ markedly from that obtained by actual measurement over the ground in 1824–5. A couple of inches would not have mattered, but it was a case of a wholly unacceptable three feet. Something had gone badly wrong.

  Everest’s suspicions immediately focused on Dinwiddie’s chain, the one used throughout by Lambton and the one on which he himself had relied for the Sironj measurement. If the error lay in the Sironj base, it could be discovered by remeasuring the base with the new compensation bars. But the bars were in store at Hathipaon. Trundling them the 450 miles down to Sironj would have to wait until after the 1837 monsoon.

  Meanwhile an attempt was made to set up the two ‘Astronomical Circles’. These instruments, specially made while Everest was in England, dwarfed even the Great Theodolite and were to be used for the final astronomical observations to establish the latitude and longitude of the Arc’s extremities. But the test-run proved to be another dismal failure. When erected, the Circles were found to be insufficiently stable and had to be carted back to the Hathipaon workshops for modification.

  By December 1837 the Survey and the compensation bars had made the forty-day trek back down to Sironj. Remeasurement of the base-line began immediately, but under Waugh’s direction rather than Everest’s. The Major’s worst fears were being realised. Another catalogue of grisly symptoms had again confined him to his tent and its adjacent ‘Necessary’. ‘Dreadful rheumatic pains in my bones – fever – loss of appetite – indigestion – intestines totally deranged – stomach totally powerless – my strength entirely gone – the whole system apparently destroyed and for ever undermined.’ He languished in his tent, not so much a caged lion as a cowed one. In marked contrast to the earlier measurement at Sironj, he declared himself hopeful, indeed touchingly confident, of his subordinates’ abilities to conduct the operation on their own. In fact they were ‘so thoroughly masters, each of his own part, that the measurement … proceeded just as satisfactorily as if I had been personally superintending it’. This was not the Everest of old. Weathered by age, achievement and ill-health, the Major was mellowing.

  The compensation bars in due course produced a measurement for the seven and a quarter miles which differed from that obtained with Dinwiddie’s chain by 2.79 feet. Thus the entire discrepancy, save for 6.395 inches, was accounted for. Everest would join in the general delight: ‘considering that the Sironj and Dehra Dun bases are separated by nearly 450 miles and 86 principal triangles, [it] is as gratifying a proof of the accuracy of the series as could be desired.’

  But to what extent he appreciated this triumph at the time is uncertain. Physically he was indeed recovering, but mentally Sironj was again taking its toll. To his ‘indescribable dismay’ he now found that not only was his eyesight affected but that his memory ‘was in a great measure gone’. He was oppressed by ‘a dreadful foreboding of ill’. It haunted his sleep and during waking hours took the form of ‘some spectre or monster of the fancy coming to hold converse with me’. ‘I thought it would certainly have ended in madness. Indeed I have little doubt that it would have … if I had not come to a better climate and foresworn business to a great extent.’

  The better climate was that of Hathipaon and the Dun. Everest’s days in the field were almost over. While he concentrated increasingly on supervising the astronomical operations and computing the results, the final observations for the Great Arc would be made by his sorely tried but now genuinely trusted assistants under Waugh as Assistant Superintendent.

  The remaining tasks included the vertical triangulation of the entire series from Sironj to the Dun to establish the heights of all the stations and so of the Dun base-line, an important first step for the triangulation of the Himalayan peaks. Simultaneously re-observation of the triangles south from Sironj to Hyderabad was undertaken and plans were laid to remeasure the Bidar base-line. To this end the compensation bars had been left in store at Sironj, suitably greased against corrosion with pig-fat and goose-lard and under the watchful eye of 2nd Assistant Owen Mulheran.

  That Everest had not exaggerated his mental state may be inferred from the fate of the unfortunate Mulheran. After a few solitary weeks in Sironj, he was reportedly overcome by a fit of religious mania ‘under which he successively burned off all his toes and several of his fingers in the slow fire of a candle’. Other manifestations of derangement ‘of a similar and even more lamentable nature’ included some wanton scratching of the precious bars. Fortunately they were not irrevocably damaged, and in 1841 were indeed employed to remeasure the Bidar base and thus complete remeasurement of the Arc to the same exacting standard all the way to Hyderabad, about nine hundred miles from the Dun. As for Mulheran, he too was not irrevocably discredited, although never entirely trusted. Four years later a colleague would draw attention to his curious habit of ‘coming to office immediately after the internal and external application of a quantity of brandy and salt’.

  The remeasurement of the Arc south to Bidar in Hyderabad had been undertaken to correct errors which might have resulted from the use of Dinwiddie’s now disgraced chain and other inferior instruments. If Everest had had his way, the entire Arc would have been revised right down to Cape Comorin. But the government had only reluctantly approved the remeasurement of the Bidar base and could see no reason for further revision in the name of inch-perfect geodesy. Lambton’s work was still good enough for all practical purposes.

  There was even stronger resistance to Everest’s unexpected suggestion of extending the Arc northwards. Following observations on The Chur and other nearby peaks, he had formed an ambitious plan of ‘turning the flank of the mountains’ by carrying the Arc up into western Tibet and on into Russian territory. The Chinese, who pretended to sovereignty over Tibet, would have to be persuaded to co-operate; but Everest thought that if both the Russians and the British could ‘act combinedly’, Peking’s jealousy might be ‘counteracted’. ‘An arc of the meridian extending from Cape Comorin to the northern extremity of the Russian dominions near Nova Zem-bla!’ he gasped. ‘It is a vast project certainly! Utilitarians will scoff at the bare idea and say cui bono? [‘to what good?’] Let these gentlemen prove to me the use of any earthly thing, and then I will take in hand to demonstrate the point at issue.’

  The point at issue was, of course, the shape of the world. To Everest as to Lambton, discovering the precise figure of the earth was the most basic challenge in human science. It was a far greater ‘desideratum’ than, say, locating the source of the Nile or understanding the properties of electricity. Or, indeed, discovering the world’s highest mountain. The Arc, quite apart from its cartographical, navigational and geological implications, promised the most intimate knowledge of the earth’s dimensions; and if knowledge was the prerequisite of mastery, on it rested the future progress of man’s management of his planet.

  With the two great Astronomical Circles reinforced and installed in specially built observatories, Waugh at Sironj and Everest at Kaliana (near the northern end of the Arc but sufficiently removed from the mountains to eliminate their ‘attraction’) laboured simultaneously on forty-eight consecutive nights in December and January 1839–40 to observe some thirty-six pre-selected stars every night. In 1840–1 the same procedure was followed at Bidar and Sironj. So satisfied was Everest with these two sections of the Arc that he was pleased to note that there were now ‘no two elements in nature more definiti
vely known’.

  Simultaneous observations of the same stars using identical instruments and procedures was the surest way of getting precise comparative latitudes. From the grand total of over three thousand stellar observations, the latitudes of Bidar, Sironj and Kaliana were calculated to three decimal points of a second of a minute of a degree. The length of the Arc could now be deduced to the same standard of accuracy, and this value then correlated with the distance as computed by triangulation to obtain the ‘amplitude’ of the Arc.

  In various reports and submissions Everest devoted reams of handwritten sheets to explaining his methods, to dilating in minute detail on the problems of refraction, plummet attraction and astronomical observation, and to recording his findings. A new set of constants – ‘Everest’s 2nd Constants’ – were issued and showed that a semi-diameter of the equator at nearly twenty-one million feet exceeded the northern hemisphere’s diameter by exactly 67,260 feet. The compression of the poles in terms of the diameter of the equator was thus 1:311.044.

  But cui bono? indeed. Basically it was all numbers, page after page of angle tables and thirty-line equations involving every logarithmic device and geometrical formula known to mathematics. ‘He undervalues everything that is not abstruse,’ complained Sir Henry Lawrence, then a rising star in the administrative firmament. Instead of surveying India, the Surveyor-General sought only ‘to astonish the savants of Europe’. The government wanted maps, or at least the coordinates for all Everest’s trig stations on which they could be based. To them, as to most other people, all the rest was just too esoteric and too incomprehensible.

  It was also too impermanent. Revisions seemed to go on indefinitely. At the mention of a new value for, say, refraction, or a new calculation of the co-ordinates for Madras, the whole thing required re-adjustment. The advent of the electric telegraph in the 1860s, and the opportunity this would provide for synchronising observations and so obtaining much more accurate readings for longitude, would constitute a veritable revolution in cartography and again necessitate extensive revision.

  When in 1843, with the Arc completed, Everest finally put Hathipaon on the market and, embracing retirement, headed home, the Great Trigonometrical Survey was going from strength to strength. More regions, notably in what is now Pakistan, came under British rule and necessitated more chains of triangles. But of the Great Arc and its champion few traces would remain. ‘No scientific man ever had a greater monument to his memory than the Great Meridional Arc of India,’ wrote Sir Clements Markham, President of London’s Royal Geographical Society; it was ‘one of the most stupendous works in the whole history of science’. Yet for a total expenditure of about £150,000 the Great Arc had left precious little to show for itself. Sixteen weather-streaked towers still dotted the Doab, three largely deserted observatories in out-of-the-way places remained to puzzle the passing traveller, and atop a variety of droogs, hills and mounds several hundred station markers slowly succumbed to the combined assault of climate, vegetation and local prejudice.

  Lambton’s uninviting reports survive only in the dusty pages of Asiatick Researches, while Everest’s two published accounts, though heavy and handsome, were poorly distributed and soon superseded. They are now unobtainable in all but a few specialist libraries. Much the most eloquent testimony to his life’s obsession lies in the ruined shell of Hathipaon on its ridge above the Dun. There he spent his last years in India, dreading the health risks of a return to the plains, working on his reports and tables, and overseeing the operations of his subordinates. From the likes of Joshua de Penning in Calcutta, of Joseph Olliver and William Rossenrode, he now enjoyed the regard and affection which he had so often forfeited.

  Both Rossenrode and Olliver had retired as soon as the Arc was finished but, with their sons and sons-in-law established in the Survey, they remained in close touch. As for old Joshua de Penning, the one-time incompetent and traitor, he had become ‘my dear old friend’. De Penning would outlast even Everest, not retiring until 1845. In a letter from Calcutta of 1841 he fusses over Everest’s health much like a loyal family retainer, and sends ‘merino vests and drawers, a dozen of each … packed up in four tin cases, which I hope will reach you in time for the cold season’. If Hathipaon has a ghost, he may be sporting woolly underwear. Perhaps, chanting logarithms from a windowless socket in what was once the drawing room, he gazes on the roofs of the Survey’s Dehra Dun offices and then, swivelling like a theodolite, fixes unerringly on the spot known as Arcadia. With Hathipaon at the apex, the site of his terminal base-line on one side and the Dehra Dun headquarters of the Survey on the other make as neat and evocative a triangle as any in India.

  ELEVEN

  A Stupendous Snowy Mass

  In the mid-1830s, while Everest and Waugh had been putting the finishing touches to the Great Arc, four other parties from the Great Trigonometrical Survey had begun work on the ‘bars’ of Everest’s cage-like ‘grid-iron’ of triangulation. In the 1840s, with the Arc complete, all resources were switched to this grid-iron and elaborate plans laid for its extension throughout the subcontinent.

  Lambton’s ‘cobweb’ of triangles in the south, though less neat and systematic than a grid, had provided the desired scatter of precisely located trig points from which cheaper topographical surveys could plot the detail needed for maps. The grid-iron was designed to furnish the same control for the rest of India, but with the trig points being arranged in ‘bars’ of triangulation.

  A less contentious analogy was sometimes drawn from nature. Envisaging the north – south Great Arc as a tree-trunk, and its east – west limbs (like the Bombay and Calcutta longitudinal series) as branches, a tracery of slender fronds festooned with triangulated foliage (the ‘bars’ of the ‘grid-iron’) were to be superimposed on the subcontinent. Extending outwards from the Arc, the shade of their branches would define what the British deemed to be India in terms more organic (and so capable of further growth) and more congenial to tender consciences.

  The immediate priority was to extend the control afforded by trigonometrical surveying to that part of northern India, the heartland of British rule, between the Great Arc in the west and Calcutta in the east. Joseph Olliver’s seven-hundred-mile longitudinal series from Sironj to Calcutta, the one conducted during Everest’s absence in England, provided the branch. Striking off from it at right angles, each ‘bar’ or ‘twig’ was to run north, roughly parallel to the Great Arc and at intervals of one degree longitude apart. With the Great Arc on the 78-degree meridian and Calcutta on the 89th, that meant eleven meridional series. Those at either end could be extended up into the Himalayas in the west, in the now British territories of Garhwal and Kumaon where Hodgson and Herbert had operated, and, in the east, into the Kingdom of Sikkim whose ruler permitted limited access to the area around Darjeeling. But for the most part the ‘bars’ terminated on the Nepal frontier, whence all approaches to the central Himalayas were still refused by the Kathmandu government.

  With the exception of these extremities, the terrain over which the new tracery extended was that of the flat, densely populated and, in those days, generously shaded Gangetic plain. Here, because of the difficulties encountered by Everest with his flares and scaffolds, smaller triangles with shorter sides than those of the Great Arc were acceptable; but sight-lines had still to be laboriously ascertained and cleared, and innumerable stumpy towers erected. Nor was the work any less perilous. On the Nepal frontier, in the dreaded terai where Robert Colebrooke had once been stricken with malaria, whole survey parties now shared his fate. The death toll amongst both British and Indians sometimes reached three figures in a single season. The danger, wrote Clements Markham of the Royal Geographical Society, was ‘greater than that encountered on a battle-field [and] the per-centage of deaths larger; while the sort of courage … required was of a far higher order’.

  Casualties in the terai attended not just the eleven south – north series, which terminated amongst its wooded swamps and grasslands,
but also a west – east series which, connecting the heads of the eleven meridional ‘bars’, was carried right through the terai. Known as the North-East Longitudinal series, it corresponded to Olliver’s Sironj-Calcutta series at the southern end of the ‘bars’. It would link their northern extremities by way of a 750-mile chain of triangles which ran parallel to the Himalayas from Everest’s base-line in the Dun all the way to Assam.

  Uniquely, the North-East Longitudinal was not, however, the work of one man or one party. None could have survived so many consecutive seasons exposed to its lethal conditions. Instead, each of the grid-iron’s survey parties, having carried their triangles north to form one of the ‘bars’, then turned left to connect it up with the top of the next ‘bar’ one degree to the west. The North-East Longitudinal was thus pieced together over many years as each of the ‘bars’ was completed. It formed, as it were, the topmost branch of the whole tree. And in its carefully triangulated trig stations running along the base of the Himalayas there lay the long-awaited certainties from which the heights of the snowy peaks might at last be confidently observed.