Radhanath Sikdar, Chief Computer of the Great Trigonometrical Survey, and the Six Plains Stations That Gave Peak XV a Mean Height of 29,002 Feet

Six observing stations on the plains of Bihar and Bengal sighted an unnamed Himalayan summit between 27 November 1849 and 17 January 1850, and the six heights they produced averaged 29,002.3 feet. Surveyor General Andrew Waugh gave 29,002 feet in a letter dated Dehra, 1 March 1856, and proposed the name Everest for the peak, which the Survey’s records called Peak XV. One of the people who turned the Survey’s field books into numbers was Radhanath Sikdar, the Calcutta-born mathematician who headed its computing department.

What Sikdar did for the Survey is documented. How much of the Peak XV figure he calculated is argued over, and this article keeps the two apart.

How a survey tells a tall peak from a near one

The Survey’s field officers worked along a chain of triangulation stations that ran east across the plains of Oudh and Bengal from 1848. S. G. Burrard, a Survey officer, described the problem in Nature in 1904. From any one station a snow peak shows its direction and its angle above the horizon, but not whether it looks tall because it is high or because it is near.

Waugh’s standing order, in Burrard’s account, was that every visible peak be observed from every station. Identifying which peak was which was left to the computers in the Survey’s offices. Waugh had trained his theodolite on the mountains from the Darjeeling area in 1847 (the hill town now reached by the Darjeeling Himalayan Railway), according to Ashish Lahiri’s summary of John Keay’s history. Another observer logged an obscure distant peak from Muzaffarpur in Bihar that November, and Waugh doubted the result because of the distance.

Burrard set out the matching procedure in four steps:

• Plot each station on a map and draw a line along every peak sighted from it.
• Where lines from three or more stations meet, assume one peak was seen each time.
• Calculate the distance from each station to that point, and from the distances an independent latitude and longitude.
• Use the angle of elevation and the distance to get a separate height from each station, and accept the identification only if the heights agree.

Peak XV passed all four tests. In Burrard’s words, the observers never suspected they were looking at the highest point on Earth.

What the six stations recorded

Burrard’s table, taken from the Survey’s records, lists the six stations by name and date. Jirol was observed on 27 November 1849, Mirzapur on 5 and 6 December, Janjpati on 8 and 9 December, Ladnia on 12 December, Harpur on 17 and 18 December, and Minai on 17 January 1850. The heights came out at 28,991.6, 29,005.3, 29,001.8, 28,998.6, 29,026.1 and 28,990.4 feet, with a mean of 29,002.3.

Lahiri, citing J. R. Smith’s biography of George Everest, says every one of the six stations lay more than 100 miles from the peak. Waugh’s letter makes the same point from the other side: the independent heights agreed more closely than he had expected, he wrote, because the mountain is massive but not a sharp, well-defined point and was seen from great distances.

Distance brings in a second correction, for refraction, the bending of light as it passes through thick air near the ground. A summit sighted from the plains looks higher than it is. Burrard and H. H. Hayden’s 1907 survey of the Himalaya says Waugh measured the bend of a light ray between the outer Himalaya and the plains of Bengal in 1853 and reduced the apparent peak heights accordingly. They add that they believed he had taken off too much.

Their own revised figure for Everest, from hill stations near Darjeeling, was 29,141 feet. They argued that 29,002 should stay in the Survey’s maps and publications anyway, because a height used as a label should not change with every refinement.

The two feet that may never have been added

Several popular accounts say the computed height was exactly 29,000 feet and that Waugh added two feet so the published figure would not look rounded. GPS World gives that version, and Explorersweb says Waugh added 0.6 metres to the computed height.

The published record points elsewhere. The table printed with Waugh’s letter gives 29,002 as the mean of the six stations, and Burrard’s table gives 29,002.3 for the same six values. Bradford Washburn’s history of Everest’s altitude calls the figure the unweighted mean of the altitudes computed from the observations. Lahiri, who read the Survey’s internal correspondence in the National Archives in New Delhi, writes that Sikdar “perhaps” showed the height would be 29,000 feet, and adds that he found no papers recording that particular calculation.

The computing office and the man who headed it

Sikdar, who lived from 1813 to 1870 according to Lahiri, was born in Calcutta, the Royal Society’s archive blog says. Rajesh Kochhar, a former director of the National Institute of Science, Technology and Development Studies in New Delhi, writes that Sikdar was a Hindu College student when he was appointed to the Survey’s computing office on 20 December 1831. Kochhar adds that George Everest kept him on in 1838 by asking for a pay rise when Sikdar wanted to leave for a teaching post, and that Sikdar retired in 1862.

A Survey Department manual credits him in print. The 1851 Manual of Surveying for India, by Captains R. Smyth and H. L. Thuillier, thanks “Babu Radhanath Sickdhar, the distinguished head of the Computing Department of the Great Trigonometrical Survey of India” in its preface. It says Chapters 15, 17 to 21 and 26 of Part III and the whole of Part V are entirely his. A passage on observing circumpolar stars adds that the formulae were investigated by him and are used in all the Survey’s rigorous computations.

Sources differ on when he became chief computer. Kochhar gives 1845, Lahiri says 1849, and the Royal Society’s archive blog says he was promoted in 1851. All of them place him at the head of the department by the time Peak XV was being computed. Kochhar, citing an archival study by Phillimore, says Sikdar and the computing office moved from the hills to Calcutta in 1849.

What the documents say about his part

Burrard’s 1904 article states that about 1852 the chief computer of the office at Calcutta told Waugh that Peak XV had been found higher than any other peak measured. He does not name the man. Lahiri reads that as Sikdar, because Sikdar held the post.

Waugh’s own 1856 letter names a different person. It credits J. Hennessey, Waugh’s assistant, for help in revising the computations, and mentions no one else. Kochhar draws on that and on Survey reports to argue that the height computations were done in Dehra Dun, away from Sikdar’s Calcutta office. He traces the story of an Indian mathematician bursting into Waugh’s room with the news to a 1928 speech by Major Kenneth Mason, reported in a newspaper and repeated by Jogesh Chandra Bagal in 1933. Kochhar writes that this rests on a single quotation, with no full text of the speech available.

Lahiri’s reading of the letters between Sikdar and Waugh gives a middle position. In his account Sikdar did no field work. The Calcutta office examined the field readings from 1849, Waugh asked him in December 1850 to revise the method of computing the positions of snow peaks seen from over 100 miles away, and a run of letters from 1851 to 1856 shows him working on method, base lines and the Darjeeling series. Lahiri also quotes a letter of 25 August 1856 in which Waugh writes that he is glad his name for the highest peak pleased Sikdar and others in the department.

Lahiri concludes that Sikdar was not the discoverer of Everest and not the only person responsible for the final computations, and that the work was done by a team. J. R. Smith, as Lahiri quotes him, also calls the computation a team effort in which Nicolson and Hennessey figured prominently. Kochhar’s article says Sikdar had no role in the height calculation. Lahiri and Kochhar read the Survey’s records differently and reach different answers.

The name, and the height since

Waugh’s letter says the Survey had always given every feature its local name, but that this mountain had none the surveyors could find and that Nepal was closed to them. He named it after his predecessor George Everest, writing “Mont Everest”. Burrard says the “Mont” never caught on. The Royal Geographical Society under Sir Roderick Murchison approved the choice, according to Burrard, while the Royal Asiatic Society backed Brian Hodgson’s claim that the peak had a local name, Devadhunga. Burrard writes that Hodgson had mistaken another peak for it. The Royal Geographical Society settled on the name Everest in 1865, per History.com and Kochhar.

The summit that Waugh named was first climbed on 29 May 1953, a day covered in the article on Tenzing Norgay. The number has moved since. B. L. Gulatee’s Survey of India work of 1952 to 1954 gave 29,028.81 feet, or 8,848 metres, the figure Washburn gives as official. On 8 December 2020 Nepal and China announced 8,848.86 metres, about 86 centimetres above the 1954 value, according to the Press Trust of India’s report in The Tribune.