The Great Arc Page 8
It is not improbable that there had been other such liaisons during his long stopovers in the field, athwart a base-line perhaps, or atop a droog. We know only of those mentioned in his estate. Kummerboo was provided for because in July 1809, with Lambton in attendance, she gave birth in Pondicherry to his first child, another ‘William Lambton’. Likewise we know of ‘Frances’ who ten years later in Hyderabad bore him a daughter and another son. Frances is described as ‘a half-caste’, perhaps Anglo-Indian or Franco-Indian. Warren hints that Lambton was debating marriage, presumably to this Frances, at the time of his death, a feasible proposition if we discount the Methuselah of tradition.
All three children were acknowledged by him and were baptised. The younger boy seems to have died in infancy, but William junior, after some elementary schooling, accompanied the Survey when in 1815 its headquarters advanced to Hyderabad and, while still only eleven, was put on the payroll as a ‘3rd Sub-Assistant’. When in 1818 a rather correct Lieutenant Everest was posted to the Survey at its then headquarters in Hyderabad, he might easily have mistaken it for a crèche. As well as young William and the pregnant Frances, Lambton’s menage included Joshua de Penning, his senior sub-assistant; Joshua’s natural son Joe, a teenager who was also about to become a 3rd Sub-Assistant; and Joshua’s wife Marie who, although only twenty-two, was already accompanied by nine of the fourteen little de Pennings she would eventually bear.
Nor was that all. Lambton’s original assistants, Warren and Kater, had since moved on, Kater to distinction in London and Warren to head the Government Observatory in Madras. Four army officers had briefly replaced them and had helped complete the triangulation in the south, but in 1811 they were withdrawn as part of a cost-cutting exercise. That left Lambton with just four lowly sub-assistants, all in their twenties and all of whom regarded his headquarters as their home. They were also all locally recruited and all, to jaundiced British eyes, socially disadvantaged because they had been born in India of at least one non-British parent.
Lambton preferred such company. Kater had been of German birth and Warren was French, though born in Italy and with Irish connections. Joshua de Penning, the most senior of these young sub-assistants, had originally come from a Madras orphanage and was perhaps Dutch by birth. Of the other three, William Rossenrode and Joseph Olliver would both, like de Penning, have long and distinguished careers in the Great Trigonometrical Survey. Moreover both had already fathered, or would soon, sons who followed in their footsteps.
Lieutenant Everest would consider himself very superior to all these ‘gentlemen’, as he called them (the word was meant to emphasise that they were not, like him, officers). Nor would they for their part easily become resigned to Everest’s notions of authority. Lambton they worshipped, but for Everest they simply worked; and if in time Everest would come to think of them and their numerous dependants as his family, it was a family which he had inherited.
Not only did Lambton recruit and train these young men, he also demonstrated the utmost confidence in them. As the Survey faced about and began extending its triangles north from Mysore into the territories of the Nizam of Hyderabad, Joshua de Penning was increasingly entrusted with the Great Theodolite and even with the primary triangulation of the Great Arc. Lambton meanwhile took the field mainly to measure base-lines and to conduct the vital astronomical observations.
Star-gazing was almost as important and certainly more demanding than triangulation. The latter simply fixed the Survey’s points of observation in relation to one another and to base-lines. But to orientate Lambton’s triangles and to establish the position of his trig points on the earth’s surface in terms of latitude and longitude, as well as to detect the earth’s variable curvature, it was essential that the survey be anchored by astronomical observations. These were usually made by measuring the angles at which planets and stars passed through the zenith as seen from the more important of his trig stations.
The more such observations from any one trig station the better. At the Tirunelveli base-line in the extreme south Lambton had spent twenty-seven consecutive nights closeted in a tent with his zenith sector (an instrument with a telescope and a giant five-foot ‘sector’ for observing these vertical angles). The result was more than two hundred astronomical observations for latitude at this one location, the mean of which could be taken to give as precise a value as circumstances allowed.
To establish the distance between two points several hundred miles apart, say at the current extremities of the Great Arc, it was important that the same stars be observed at each place, preferably at the same time and with identical instruments. This was asking a lot of the Indian climate since the monsoon in the north of the peninsula does not coincide with that in the south. It also asked a lot of the Survey’s resources and would challenge even Everest’s genius for organisation. Nevertheless, Lambton was able to make some important corrections to existing maps. The position given to the great city of Hyderabad, whence he now directed the progress of the Great Arc through the territories of the Nizam, he found to be ‘out [by] no less than eleven minutes in latitude, and upwards of thirty in longitude’.
The Observatory in Madras, where observations and records stretched back many decades and where the dependable Warren now held sway, was the starting point for all peninsular surveys. Its value in relation to the Greenwich meridian (the zero for longitude) and the equator (the zero for latitude) was the Survey’s sheet-anchor. Madras was in effect the Indian Greenwich. And when, as happened, some infinitesimal adjustment was made to the coordinates for the Madras Observatory, Lambton’s whole web of triangles had to be realigned.
Other such adjustments would necessitate further mind-boggling recalculations. A later writer estimated that the trigonometrical surveying of India involved 9,230 unknowns and produced ‘unwieldy equations exceeding anything of the kind ever attempted’. Trial and error, leading to constant refinement, played no small part in the geodesist’s science. His situation was like that of a farmer trying to sow his drill evenly with an uncertain number of seeds. When the seeds ran out before he reached the end of the drill, he must needs go back and respace them; and likewise if he came to the end with seeds to spare. Repeating and reviewing past work was as important as prosecuting new work.
For example, the length of a degree of longitude as calculated from that short arc carried south from Madras in 1802 was soon revised when the Great Arc produced a more refined value. That in turn meant that the earliest triangles based on the Madras measurement had also to be revised. As the Arc got longer, other assumptions about the curvature of the earth were reassessed, and these in turn meant more recalculation. Lambton had at first accepted Sir Isaac Newton’s figure of 1/230 for the compression of the earth’s spheroid at the poles. However this ‘constant’ proved anything but. It was revised down to 1/304 in 1812 and by Lambton himself to 1/310 when in 1818 his Great Arc had embraced nearly ten degrees of latitude. Everest in turn would come up with his own constants; and every new constant meant recalculating all previous work.
Further complications arose from attempts to refine standards of length. Lambton’s anxieties over the elasticity of Dinwiddie’s chain increased with every base-line measurement. When the chain unaccountably stopped expanding as measured against the one held in reserve, he became suspicious about the reliability of the latter as a standard. As once before, a hundred-foot brick wall was constructed, tents erected over its entire length, and its surface levelled and polished ‘so as to resemble a sheet of glass’. Both chains were then stretched along it, their relative values being assessed by micrometer against a standard bar and then marked against pre-set brass studs, mounted in lead, and set in concrete.
Matters were not assisted when in 1821 a parliamentary committee in England laid down a new standard of length. Lambton had long urged the adoption of such a standard, although he would much have preferred that based on the decimal metre and its derivatives as already calculated by the French. The Brit
ish ignored this advice. In London Henry Kater reduced the new standard to the scale used by Cary in calibrating the dial of Lambton’s Great Theodolite. Lambton had then again to go right through all his measured angles and readjust them.
It was hardly surprising that he had little time for fieldwork. As he patiently explained to the Calcutta authorities, he could not simultaneously continue the surveying and process its results. The calculations involved were so complex that they could be entrusted to no one else. Even producing a fair copy of one of his reports took five months and, because of its highly technical nature, it could not be delegated. Instead he must delegate the fieldwork. If the government were unhappy with this arrangement, they must supply him with a senior assistant; and while they were about it, he also badly needed a doctor and a geologist.
The doctor was required to minister to Lambton’s survey parties, who were continually having to quit the field because of fever, while the geologist was needed to sort out his problems with the plumb-, or plummet-, line. Although the Great Arc was providing satisfactory proof of how degrees along the meridian increased in length as he headed north, they were not increasing by any consistent value; in one case they actually decreased. Similar anomalies had been found on the arcs measured in France and England and led cynics to suggest that the surveyors were not as infallible they pretended.
But after checking and rechecking, Lambton was sufficiently confident of his own working practices and calculations to look elsewhere for an explanation. The fault, he supposed, lay in the plummet-line, whose vertical was particularly critical in observations conducted with the zenith sector. It was known that the existence of nearby hills might distort the plummet by attraction, another knotty problem as yet unforeseen by Himalayan surveyors. But Lambton now found that even when he was well clear of hills, irregularities still occurred. The worst example of deflection had been at Bangalore, which he could only ascribe to signs of a subterranean ‘vein of dense ore’. And not without a note of triumph he announced that it was this speculation which ‘discovered to us an agent unthought of in former days, viz., a disturbing force occasioned by … diversity in the density of strata under the [earth’s] surface’.
Hence the need for a geologist and hence, in time, a whole new field of geodetic experimentation in which pendulums were used to discover variations in the direction of gravity due to the variable density of the earth’s crust. These in turn would reveal that the vertical attraction exercised by mountains was compensated for, and often more than compensated for, by the greater density of the subterranean strata which supported the mountains. As with icebergs, these invisible substrata might extend well beyond that part of a mountain which was visible above ground. Plummet-lines, instead of being attracted towards visible mountain masses, were thus just as likely to be deflected away from them and towards the denser outlying sub-strata, a contradictory and compensatory effect known as ‘isostasy’. The Himalayan surveyor was in for more surprises.
In 1818 Lambton learned that he was at last to get both his geologist and his doctor, as combined in the person of Henry Voysey. In the previous year he had submitted his third report, having in 1815 completed the Great Arc up to Bidar, about eighty miles west of Hyderabad. There he laid out his sixth base-line. The Arc, now of nearly ten degrees (or over seven hundred miles), was much ‘the longest that has ever been measured on the surface of this globe’. It had overtaken even that in Europe and, like the Anglo-French arc, ‘in grandeur and accuracy [it] must be allowed to exceed anything of the kind recorded in the history of practical science’. No longer merely a curiosity, the Arc had acquired a celebrity and a momentum of its own.
Lambton, too, was becoming something of a legend. In belated recognition of his achievement, the Survey, hitherto variously known as the ‘trigonometrical’, ‘astronomical’, or ‘mathematical’ survey of Mysore – or sometimes simply as ‘Lambton’s’ – was now officially designated as The Great Trigonometrical Survey of India. And in recognition of its having passed beyond the territories controlled from Madras it was transferred from the Madras government to the supreme government in Calcutta and to the personal attentions of the Governor-General. First intended just to cover Mysore, it had since been extended to the whole peninsula, and now in 1818 it was hoped that it might be continued north, east and west at least until lateral chains of triangles could link Bombay and Calcutta.
This meant extending the Great Arc itself still further. Lambton’s initial ‘foray’ into the more unruly territories of the Nizam of Hyderabad had gone smoothly enough. Provided he could evade the ‘gangs of plunderers which infest that part of the country when the army is not in the field’, he planned to continue following the same 78-degree meridian through the northern districts of Hyderabad and on to Nagpur in central India. ‘Should I live to accomplish that,’ he wrote, ‘there will then be a foundation for extending the survey over the whole of the Deccan … through the Maratha dominions … and finally into the upper districts of Hindustan [i.e. north India].’ The government endorsed this proposal by suggesting Agra on the edge of the Gangetic plain as a suitable termination.
But Lambton, possibly into his forties when he started on the Survey, had by now been in the field for sixteen years. Whatever his real age, he was beginning to show it. His few remaining hairs were grey, his formidable stamina a wheezing shadow of its old self. Despite his eagerness to carry the work forward, even he was giving serious thought to a successor.
I sincerely hope, that after I relinquish [the Survey] some one will be found possessing zeal, constitution and attainments wherewith to prosecute it on the principles already followed – It would indeed be gratifying to me if I could but entertain a distant hope, that a work which I began, and which will then be brought to so considerable a magnitude, should at some future date be extended over British India.
The hint was taken. In 1818, as well as Dr Voysey, Lambton was also awarded the services of a senior assistant; and it was thus that, on Boxing Day of that year, there rode into Lambton’s no doubt riotously festive compound in Hyderabad a clean-shaven and mustard-keen Lieutenant George Everest.
By his own account, Everest approached ‘the great man’ with deference. Simple manners and reclusive habits did not mean that Lambton was indifferent to recognition and, though long delayed, fame had eventually caught up with him. The Astronomer Royal’s letter in 1806 had been followed by an authoritative and highly flattering article of 1813 in the Edinburgh Review. Penned by Professor Playfair, it carefully elucidated Lambton’s work, applauded his extraordinary dedication, and favourably compared both to those of William Roy, Lambton’s original inspiration. In fact Roy and Lambton were jointly hailed as ‘doing more for the advancement of general science than had ever been performed by any other body of military men’.
Unaccountably, the scientific establishment in London had not immediately responded. Lambton, unlike Everest, had few distinguished connections and was a stranger to the wiles of self-promotion. But in 1815 his old friend and one-time assistant John Warren had headed home to France. With Napoleon’s defeat and the restoration of the French monarchy Warren sought a reunion with his family. Coincidentally he was also reunited in Paris with his old Colonel, Arthur Wellesley, fresh from victory at Waterloo. Reinstated in the French army and recognised as the 24th Comte de Warenne, Warren soon alerted the scientific authorities in Paris to Lambton’s work.
Rightly the French regarded geodetic discovery much as the British were coming to regard geographic discovery. They were the pioneers and the arbiters; it was their science, and in Lambton’s labours they generously recognised a worthy fellow-worker. In 1817 Jean-Baptiste Delambre, the eminent astronomer, joined Pierre La Place, a leading geodesist whose theorem for spherical excess Lambton had used, in sending him glowing tributes and extending to him the highest honour of a corresponding membership of the French Academy of Sciences.
This recognition finally prodded the Royal Society in London into off
ering him an honorary fellowship. The East India Company had then followed with what Lambton regarded as a particularly pleasing letter of congratulation from one of their oldest directors. It was especially welcome because the writer was Samuel Davis, once himself a surveyor, who forty years earlier had accompanied a trade mission to Tibet. In fact his were the observations which had alerted Sir William Jones to the great width of the Himalayan chain and which had prompted Jones’s still unproven claim about the Himalayas being the world’s highest mountains.
To the young Everest, the ‘big bald’ Lambton seemed a formidable figure. He calls him ‘the great man’ and claims to have been following his progress for years. A certain eccentricity, which in others Everest would surely have censured, only added to his stature.
I shall never forget the impression which the bearing of this veteran and far-famed geodesist made on my mind when I first saw him … at one of our stations; for though we had been in camp together for some days previous, he had displayed no symptom of more than common powers, but seemed a tranquil and exceedingly good-humoured person, very fond of his joke, partial to singing glees and duets, and everything in short which tended to produce harmony and make life pass agreeably; … but when he aroused himself for the purpose of adjusting the great theodolite, he seemed like Ulysses shaking off his rags; his native energy appeared to rise superior to all infirmities, his limbs moved with the vigour of full manhood, and his high and ample forehead gave animation and dignity to a countenance beaming with intellect and beauty.