Is the city doomed?

PATRICK WATSON

Dark Age AheadBy Jane JacobsRandom House Canada,241 pages, $29.95When a London parish was hit by cholera in 1854, a physician named John Snow found not only a way to bring it instantly under control, but also a radical but simple technique for identifying the causes of epidemic disease. Dr. Snow's work is graphically reproduced in Edward Tufte's provocative book Visual Explanations (Graphic Press, 1997). What Snow did was simply to mark a map of the parish with a dot for every occurrence of cholera, until he had located a hitherto unsuspected object that was at the centre of its greatest density, a well from which every victim had taken drinking water. (Before this it was not known that contaminated water was the source of cholera.) This kind of graphic research had never been done before.