LATITUDE: THE ASTONISHING ADVENTURE THAT SHAPED THE WORLD

February 11, 2022
Posted by: ADMIRAL SIR NIGEL ESSENHIGH

Many NR readers will recall from their early navigation training that the polar diameter of the Earth is less than the equatorial equivalent, the reason being that, in Newtonian mechanics, due to centrifugal forces caused by our planet’s rotation, we live on an oblate spheroid, an ellipsoid now expressed to an accuracy of 2cm in WGS 84.  In short, the Earth is not perfectly spherical.  That we know this for certain dates not from modern mathematical and surveying techniques, but from the efforts of an 18th century expedition to the equatorial Andes in what is now Ecuador and northern Peru.

This book (a Covid lock-down project) by Nicolas Crane, a geographer and prolific author, draws on a wide variety of primary and secondary source material to re-tell the story of this expedition whose primary aim was to determine the length of a degree of latitude at the Equator which, in turn, could be compared to both the theoretical 60 miles and to a similar actual measurement near the North Pole. The object was to gather data accurate enough to determine whether the Earth was elongated towards the poles (prolate) as the Cartesian followers believed, or was it flattened at the poles (oblate) as Newton proposed. As we now know, the Newtonian proposition won the day.  However, here we read of the extraordinary difficulties that were encountered by this disparate, 10-strong French and Spanish team of academicians, scientists and sundry others including an entourage of servants, slaves, porters, and muleteers.  The plan was to establish a very accurate baseline to the north of Quito, itself very close to the Equator, and then construct a network of triangulation, southwards for 3 degrees of latitude between the Eastern and Western Cordilleras of the Andes using markers placed on various mountains and volcanoes.  Easy one might think.  However, the sheer enormity and difficulty of the project only became apparent when the job was tackled.  The team was ill-matched, temperamentally unsuited to teamwork and, from the outset, was poorly led.   From when they departed Rochefort in May 1735 until they returned in dribs and drabs between 1744 and 1745, some never returning to France, for over nearly 10 years away they dealt with incompetence, inadequate funding, corruption, political strife, mutiny, violence, murder, disease, endless delays in adverse weather in both tropical heat and Andean cold, plus incessant internal squabbling within the group.

The triangulation process was extraordinarily difficult and involved herculean efforts to transport the sensitive equipment over the most challenging terrain and involved some feats of mountaineering to establish trigonometric marks.  However, the product was an astonishingly accurate set of data plus incidental outputs far beyond geodesy.  This included information covering magnetism, gravity, and the speed of sound as well as the discovery of rubber, the identification of the bark of a tree which produced quinine that had a major impact on the prevention of malaria, the discovery of platinum, the first accurate mapping of a major Inca site and a very detailed and accurate map of the city of Quito which has served to illustrate the nature of Spanish colonial settlement in South America.  An interesting by-product from one of the Spanish members was a comprehensive, confidential report on the ills of colonial Spain.

Your reviewer is a self-confessed and unrepentant navigational nerd and thus found the detailed discussions of geodesy to be particularly interesting.  Less encumbered readers should not be distracted by this detail nor by the many colloquialisms which would have benefitted from more ruthless application of the editorial red pen. This account is more than anything a tale of dogged human triumph over adversity and, indeed, a most gripping adventure story.