I got the last issue of The Economist on Monday. One of the articles I read the same day is about the pollution of the Great Lakes in the States: Michigan, Huron, Eerie, Ontario, and Superior. Together, they comprise one-fifth of the world’s surface fresh water. Ever since the Seventeenth Century, industrial plants processing timber, iron, grain, and coal lined the shores of the lakes, using water as a coolant. The pollution eventually reached such stupendous levels that the Cuyahoga River, which empties into Lake Eerie, caught fire forty years ago this month. It is Wednesday, but the image is still pulsating through my mind: the Cuyahoga in flames.