Crowds have always puzzled historians. As essentially anonymous and spontaneous movements, they often seem to possess a mysterious, irrational, and even primal quality. They can form suddenly and unpredictably, unite strangers behind an apparently common cause, move through the streets as if acting with a single will, and then unexpectedly melt away into the surrounding neighborhoods and markets from which they came. Explanations are not easy to find. Once the sound and fury have subsided and participants have left the streets, it is nearly impossible to trace identities or determine individual motives for joining demonstrations. This obscurity only deepens when one moves to the more distant past, as the number of records and firsthand accounts rapidly dwindles.