The Great Arc is a fascinating account of how an arc of longitude was measured starting from Cape Comorin at the southern tip of the Indian subcontinent northwards to Hyderabad, and continuing to Dehra Dun in the Himalayas; how this helped to deduce what sort of spheroid the Earth is, and how one of the surveyors who took part in this Great Trigonometrical Survey got to place his name just a little nearer to the stars than that of any other mapmaker. I admire the persistence of these men, their determination to keep going in spite of the difficulties of the terrain, the fevers, the tigers, and finally the cold and the violence of the wind in the Himalayas. Recommended to all lovers of maps.