At the time Madras, although relieved of the French challenge from Pondicherry, confronted an Indian challenge from the expansive ambitions of an upcountry neighbour in the state of Mysore, roughly the modern Karnataka. There ensued no fewer than four Anglo – Mysore Wars, that of the Wellesleys and Lambton being the Fourth. It was also much the most one-sided. The gauntlet first thrown down in the 1760s–80s by Mysore’s Haidar Ali, a formidable campaigner, had come to look more like a glove-puppet when tossed into the ring in the 1790s by his quixotic son Tipu Sultan. By then the British, buoyed by their successes in Bengal, were capable of overwhelming any opposition and happily construed all but abject compliance as punishable defiance.
Tipu Sultan had counted on French support. To this end he had reversed the one-way traffic of colonial diplomacy by despatching an impressive mission to Versailles. It had arrived in France in 1788 only to find Louis XVI desperately trying to stave off his own crisis – the deluge which within a year would plunge France into Revolution. No Franco – Mysore alliance resulted, and in India Tipu now stood alone against the mighty concentration of British power. He remained defiant. Dubbed the ‘Tiger of Mysore’, he delighted in a working model, complete with sound effects, of a tiger devouring an English soldier (now in London’s Victoria and Albert Museum). But in the Third Anglo – Mysore War of 1790 it was the tiger who was severely mauled; and in the Fourth of 1799 it remained only to despatch him.
Lambton played his part in this war with distinction. By consulting the stars he was able to avert a disaster when during a night march General Baird mistakenly led his column south towards enemy lines rather than north to safety; and at the great set-piece siege of Tipu’s stronghold at Srirangapatnam he set a rather better example of derring-do than the future ‘Iron Duke’. The war itself, waged with such overwhelming superiority, proved little more than the expected tiger-hunt. It lasted just four months. Srirangapatnam was ravaged with an ardour worthy of Attila the Hun, and Tipu was found slain amongst the ruins.
Rounding up the spoils took longer and was much more gratifying. The territories of Mysore stretched across peninsular India as far as the west, or Malabar, coast and south almost to its tip. Following Calcutta’s example in Bengal, Madras had at last acquired a sizeable hinterland of Indian real estate, most of which would henceforth be directly ruled by the British.
It was while travelling with Arthur Wellesley and his staff across this fine upland country of teak woods and dry pasture, subduing a recalcitrant chief here and plundering a fortress there, that Lambton conceived his great idea.
As when New Brunswick was settled, the country was virtually unknown to the British. To define it, defend it and exploit it, maps were desperately needed, and two survey parties duly took the field in 1799–1800. One concentrated on amassing data about crops and commerce. Its three-volume report, a rambling classic of its kind, would include such gems as an account of cochineal farming – or rather ranching, for the small red spiders from which the dye is extracted required only tracking and culling as they spun their way along the hedgerows, multiplying prodigiously.
The other survey was a more formal affair, similar to surveys already undertaken in Bengal. It was equipped with theodolites for triangulation, with plane-tables for plotting the topographic detail, and with wheeled perambulators and steel chains for ground measurement. Colonel Colin Mackenzie, who conducted it, was another noted mathematician who had originally forsaken his home in the Hebridean Isle of Lewis to visit India in order to study the Hindu system of logarithms. His Mysore Survey was a model of accuracy and the maps which it yielded faithfully delineated the frontiers of the state as well as indicating ‘the position of every town, fort, village … all the rivers and their courses, the roads, the lakes, tanks [reservoirs], defiles, mountains, and every remarkable object, feature, and property of the country’. Additionally, Mackenzie collected information on climate and soils, plants, minerals, peoples and antiquities. The last was his speciality. In the course of the Mysore Survey and other travels, he amassed the largest ever collection of Oriental manuscripts, coins, inscriptions and records. Congesting the archives of both India and Britain, the Mackenzie Collection was still being catalogued a hundred years later.
Under the circumstances, Lambton’s big idea to launch yet a third survey looked like a case of overkill; and with Mackenzie’s efforts promising to make Mysore the best-mapped tract in India, Lambton anticipated official resistance. But as Arthur Wellesley now appreciated, his subordinate was proposing not a map, more a measurement, an exercise not just in geography but in geodesy.
Geodesy is the study of the earth’s shape, and it now appeared that while holed up through a dozen long Canadian winters Lambton had made it his speciality. Studying voraciously, reading and digesting all the leading scientific publications, he had taken a particular interest in the work of William Roy, founder of the British Ordnance Survey, and of Roy’s even more distinguished mentors in France.
Surveying of a basic nature had been among Lambton’s early responsibilities in Canada. Some old maps of New Brunswick actually show a ‘Lambton’s Mountain’. It is not very high and the name, unlike Everest’s, would not stick. Instead it became ‘Big Bald Mountain’ – which was more or less what Lambton would also become. But such surveying, although based on the simple logic of triangulation, was child’s play compared to what the Cassini family in France and William Roy in Scotland and England had been attempting.
Triangulation, together with all its equations and theorems (like that of Pythagoras), is strictly two-dimensional. It assumes that all measurements are being conducted on a plane, or level surface, be it a coastal delta or a sheet of paper. In practice, of course, all terrain includes hills and depressions. But these too can be trigonometrically deduced by considering the surface of the earth in cross-section and composing what are in effect vertical triangles. The angle of elevation between the horizontal and a sight-line to any elevated point can then be measured and, given the distance of the elevated point, its height may be calculated in much the same way as with the angles on a horizontal plane. Thus would all mountain heights be deduced, including eventually those of the Himalayas. Adding a third dimension was not in theory a problem.
However, a far greater complication arose from the fact that the earth, as well as being uneven, is round. This means that the angles of any triangle on its horizontal but rounded surface do not, as on a level plane, add up to 180 degrees. Instead they are slightly opened by the curvature and so come to something slightly more than 180 degrees. This difference is known as the spherical excess, and it has to be deducted from the angles measured before any conclusions can be drawn from them.
For a local survey of a few hundred square miles the discrepancies which were found to result from spherical excess scarcely mattered. They could anyway be approximately allocated throughout the measurement after careful observation of the actual latitude and longitude at the extremities of the survey. This was how Mackenzie operated. But such rough-and-ready reckoning was quite unsatisfactory for a survey of several thousand square miles (since any error would be rapidly compounded); and it was anathema to a survey with any pretensions to great accuracy.
The simplest solution, as proposed by geographers of the ancient world, was to work out a radius and circumference for the earth and deduce from them a standard correction for spherical excess which might then be applied throughout any triangulation. But here arose another and still greater problem. The earth, although round, had been found to be not perfectly round. Astronomers and surveyors in the seventeenth century had reluctantly come to accept that it was not a true sphere but an ellipsoid or spheroid, a ‘sort-of sphere’. Exactly what sort of sphere, what shape of spheroid, was long a matter of dispute. Was it flatter at the sides, like an upright egg, or at the top, like a grapefruit? And how much flatter?
Happily, by Lambton’s day the question of the egg versus the grapefruit had been