The Measure Of All Things by Ken Alder The Free Press $145 WRITING GOOD scientific history is difficult. But Ken Alder bridges the gap between fact and entertainment brilliantly in this often witty expose of an intriguing scandal that throws doubt on the veracity of one of the fundamental cornerstones of measurement: the metre. It is a tale of political, social and economic intrigue set against the dramatic backdrop of revolutionary France. When, in the dying days of the French monarchy in 1792, two scientists were dispatched from Paris by the Academy of Sciences to gather data to determine the exact length of a true metre, their journey of seven years was to be one of self-discovery as they battled pride and ego as much as doubting colleagues and suspicious compatriots. Their mission was to measure the world. The method they used sought to confirm and legitimise the work of an earlier expedition by recording the exact length of the meridian from Dunkerque to Barcelona. From this their task was to establish a new measure, the metre, as one ten-millionth of the distance from the North Pole to the Equator. Alder cycled the route for background and while it is a pity he does not make more of this, he describes how the two men overcame innumerable obstacles to take painstaking measurements with precision instruments using geodesy - a method based on Euclidean geometry. Joseph Delambre, a bachelor, was a cosmopolitan, self-educated humanist whose extrovert nature hid a determination to seek truth through scientific discovery. Heading in the opposite direction to lead the southern portion of the expedition was Andre Mechain. His studious seriousness and historical links to the Academy of Sciences were to lead to an agonising examination of conscience. Both were driven by duty, honour and service to their country. But France was in turmoil and at war with itself and its neighbours. Alder traces how various conferences and governments eventually collaborated and helped develop the metric system. The benefits of which to trade and industry are enjoyed by many nations, with the significant exception of the United States. The story of why the US refused to conform is worth the price of the book alone. The rest tells of a captivating adventure illuminating a period of European history characterised by dissent and disruption. In the end it does not matter that the French team's original metre was two millimetres short. It was the determination of the two to pursue the concept of a universal measure that remains the bedrock of modern measurement. The errors of the past can shape the direction of science as much as the truth. The metre is a useful fiction.