BOOKS

Mapping India under the Raj

The Great Arc by John Keay; HarperCollins Publishers, London, 2000; pages 182 (paperback), £6.99 (in India: Rupa and Co. under special price of £3.95).

THIS is a fascinating account of a unique and arduous scientific expedition undertaken in the Indian subcontinent in the 19th century under the British Raj. "The Great Indian Arc of the Meridian", as the odyssey was named and from which the book derives its title, has been hailed as "one of the most stupendous works in the whole of history of science" and "as near perfect a thing of its kind as has ever been undertaken". April 2002 marked the bicentenary of that gigantic experiment that lasted nearly half a century (Frontline, May 10, 2002).

One of the unsettled scientific questions in the late 18th century was the exact nature of the shape of the earth. While it was generally known that the earth was not a sphere but an 'oblate spheroid', more curved at the equator and flatter at the poles, the question of 'how much more' was yet to be established. One way of doing that is to determine the length of the arc along a chosen longitude or meridian at one degree latitude separation. The length of one degree arc would be less near the equatorial latitudes than at the poles. This fact was established in the 1730s by French survey expeditions to Ecuador near the Equator and Lapland in the Arctic, which found that around the middle of the earth the arc was about a kilometre shorter.

The Great Arc experiment was launched primarily to do a similar measurement in the tropical latitudes and do it better by measuring the distance over a longer arc in the Indian subcontinent. The basic idea was to determine how regular the 'oblateness' was and from the measurement gain more precise knowledge of the shape of the earth. Conceived by Colonel William Lambton, an engineer, a mathematician, an astronomer and a surveyor with an abiding interest in geodesy, whom John Keay calls a "genial genius", the project was proposed in 1799 and approved in 1800.

Lambton, along with his band of surveyors and assistants, and equipped with, among other things, carriages, palanquins, tents and a massive half-tonne theodolite specially ordered from London, began his mission on April 10, 1802, with the first 7.5 mile baseline measurement between St. Thomas Mount in Madras and another chosen spot to its south. This measurement alone took 57 days.

What began as an attempt to measure an arc confined to the southern peninsula - from the tip of the subcontinent Kanyakumari to 18° latitude near Hyderabad along the 78° meridian - that would yield the 'length of a degree of latitude', the potential utility of extending the arc further up north along the 78° meridian became obvious to Lambton. The Great Arc would serve as the "trunk of a tree" or the "spinal column of the skeleton" that would embrace the entire country and could be used as the basis and benchmark for regional surveys - the Madras Survey, the Bengal Survey and the Bombay Survey - which were being carried out with the expanding control and influence of the Raj. The Great Arc would enable the mapping of the entire country mirroring the progress of the empire, as it were. The Great Arc gave rise to the Great Indian Trigono- metrical Survey.

After Lambton's death midway through his mission in 1823, the Great Arc was carried forward from Nagpur right up to the first range of the Himalayas near Mussoorie by, in the words of Keay, the "bewhiskered and cantankerous martinet" lieutenant George Everest, who had joined Lambton in the year 1818. The total north-south distance of about 1,600 miles (2,575 km) was the longest measurement of the earth's surface ever attempted, which was completed in 1843. As Keay observes, it is indeed curious that neither of the two pioneers figures with any prominence in historical accounts of either science or the empire. "Lambton is not even among the fifteen thousand worthies included in Chambers' Biographical Dictionary. Everest is just a mountain," rues Keay.

As the subtitle of the book says, the story of The Great Arc is indeed "the dramatic tale of how India was mapped and Everest was named, how the dedicated team of intrepid surveyors undertook this 40-year long high-risk journey, braving bouts of malarial fevers, dysentery, floods and inhospitable weather, through hills, jungles and swamps.

Keay narrates this story beautifully and in an engrossing manner. He also succeeds in conveying the technical aspects of geodesy and surveying with simplicity and lucidity. If you want to understand what a theodolite is or what 'triangulation' is or how a network of imaginary triangles results in a cartographic map, it is all there without the dramatic thread being lost or weakened.

Keay was perhaps ideally suited to reconstruct the events of the Great Arc given his deep knowledge of the British Empire and his writings on the East India Company and related histories of Asia and South East Asia. As he notes in the preface, "In writing this book, the challenge has not been that of embroidering the bare facts with vivid shades of plausible detail" - which he does in a remarkable manner - "of stitching into the riot of authentic adventure a thread of scientific and political plausibility." While the book is essentially about the unique scientific enterprise and about surveying and measuring the subcontinent, Keay does not fail to place The Great Arc in its correct political context and setting, albeit only obliquely.

Consider this passage: "It would be unfair to claim that the Rebellion, like the measurement of Mount Everest, stemmed from the Great Trigonometrical Survey. But surveyors had undoubtedly fuelled both the British sense of superiority and Indian sense of grievance. 'Bars' and 'chains' of invisible triangulation looked and sounded a lot like political strangulation. Not unwittingly, the Survey had furnished the paradigm and encouraged the mind-set of an autocratic and unresponsive imperialism. Additionally, the razing of whole villages, appropriating sacred hills, exhausting local supplies, antagonising protective husbands and facilitating the assessment of the dreaded land revenue, the surveyors had probably done as much to advertise the realities of British rule and so alienate grassroots opinion as had any branch of the administration."

THE genesis of this book is quite interesting. Not many would have given serious thought to the question why the highest peak in the world was so named when most high peaks of the Himalayan range have either native names such as Nanda Devi, Nanga Parbat, Kanchenjunga and Masherbrum or, where native names do not exist, designated by some alphabet like K2. Indeed, it is not even generally known that Everest is derived from a person's name (except perhaps to those in the profession of surveying) let alone the reasons for it. While working on a book on explorations in Kashmir, Keay stumbled on the name in association with the Survey of India. "And the Survey being a government department within British India's bureaucratic Leviathan," writes Keay, "it had generated copious records. To these I turned."

Keay worked back from the records of measurement of heights of Himalayan summits by 19th-century map-makers, and traced the starting point or benchmarks that provided the reference coordinates which had been determined with great precision. "I asked around, I dug out books, and the trail led back to the Great Arc," writes Keay. Like most of us he too had heard of it for the first time then. More curious is the fact that Everest himself saw the mountains only towards the end of his career. Having fulfilled the dream of the Great Arc, he was not particularly curious about the heights of Himalayan peaks even though there was the controversy then about the Himalayas being higher than the Andes. He never saw the Everest, let alone set foot on it.

But the foundation that he (and Lambton) laid, in particular the night- sighting techniques of Everest, enabled a precision measurement of these great heights by his associates after Everest returned to England in 1844. The name itself was given by his associate Andrew Scott Waugh after he, aided by the Survey's chief computer Radhanath Sikdhar, determined the correct height of what was until then designated as Peak XV. The logic in naming the highest point as Everest, as Keay writes, lay in the painstaking measurement of a meridian "up through India's burning immensity", which made possible the measurement of the ice-capped Himalayas. The credit for unearthing the origins of the name Mt. Everest goes to Keay. More pertinently, Keay points out how the name is to be pronounced as Eve-rest (as in cleave-rest) and not as Ever-rest (as in cleverest).

Far from being a dry account of a mammoth scientific endeavour, the Great Arc has an undercurrent of wry wit. Whether it is a description of some complicated measurement or some anecdote, it abounds in detail. By the time one is through with the book, the personalities of Lambton and Everest become vivid imagery, particularly of the latter whom Keay has described with great relish. In his efforts to reconstruct the lives of the two during their work on the Great Arc in as complete a manner as possible, Keay's discovery of Lambton's forsaken grave at Hinganghat in Maharashtra is particularly commendable and so is his trekking to Everest's reclusive estate at Hathipaon near Mussoorie. Both are in a state of neglect. The former would not even have been identified but for Keay's efforts. As an aside, Keay hopes that the Survey of India, with all the resources that are available to it, will restore and maintain these monuments. At least in this year of bicentenary, the government will realise Keay's hope for posterity to be aware and appreciate the invaluable contribution of the two remarkable men of geodesy to science and geography of the subcontinent.