Book Review: The Great Arc - John Keay

This book invokes two very different reactions in me. The primary reaction is jubilant, almost romantic. The second is gloomy. Imagine you’re watching Oppenheimer: spirits rising until the point the bombs actually drop, after which you feel guilty about having felt good in the first place.

The Great Trigonometric Survey was completed over the duration of a better part of a century, across three generations of mathematicians, physicists and surveyors (they were called compasswallahs - I finally see where Rohit Gupta gets his pseudonym), and at the cost of thousands of lives. They managed to complete an accurate-to-the-inch survey of much of the subcontinent. The Great Trigonometric Survey afforded to the Raj a much welcome administrative and military efficiency over the whole subcontinent. It is perhaps only a coincidence that the events of 1857 happened only a few years after the conclusion of the survey. But it’s very likely that the Survey was among the many things that irritated Indians. And the results of the Survey certainly played no small part in quelling of the Rebellion.

After all, the survey divided the whole country into a grid of triangles. The line-of-sight needed to establish the vertices of a triangle led the surveyors to cut through jungles, mountains, rivers, settlements and even temples and mosques alike in the pursuit of accuracy. There was an oversimplifying, reductive flavour to the activities of the Survey, which might have been insulting to locals. The author duly acknowledges this, too.

But the stated goal of the Survey was deceptively innocent, even admirable: they wanted to measure the shape of the earth. India was simply in the wrong place at the wrong time. It just so happened that of all the British territories in the tropics, India was the most ‘vertical’ and most varied in its landscape, and as such uniquely suited for an ambitious geodesic experiment.

What fascinates me most is that much of the Survey happened in my backyard. I’ve spent much of my life living along the very Arc of the Meridian which the GTS proposed to measure. I grew up in Nagpur. The father of the GTS, William Lambton, is buried in Hinganghat, which is just an hour south of Nagpur. I’ve spent much of my life in Delhi, with easy access to Dehradun, which is where the survey ended, which is home to the Survey General of India. I’ve spent a lot of time in Hyderabad and Chennai, where the Survey originated. It seems like the goras from 200 years ago knew my country better than I do today. And it takes a contemporary gora to write a good book about it. Of course, there’s nothing wrong with that. Only, I regret not being introduced to this massive part of our national and scientific history in high school.

Unfortunately, the responsibility of teaching the history of science and math falls neither on the high school math teacher nor on the history teacher. After all, it would be a travesty to have kids enjoying trigonometry and history.

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