<P> The subjects of Mackay's debunking include alchemy, crusades, duels, economic bubbles, fortune - telling, haunted houses, the Drummer of Tedworth, the influence of politics and religion on the shapes of beards and hair, magnetisers (influence of imagination in curing disease), murder through poisoning, prophecies, popular admiration of great thieves, popular follies of great cities, and relics . Present - day writers on economics, such as Michael Lewis and Andrew Tobias, laud the three chapters on economic bubbles . Scientist and astronomer Carl Sagan mentioned the book in his own discussion about pseudoscience, popular delusions, and hoaxes . </P> <P> In later editions, Mackay added a footnote referencing the Railway Mania of the 1840s as another "popular delusion" which was at least as important as the South Sea Bubble . Mathematician Andrew Odlyzko has pointed out, in a published lecture, that Mackay himself played a role in this economic bubble; as leader writer in the Glasgow Argus, Mackay wrote on 2 October 1845: "There is no reason whatever to fear a crash". </P> <P> Among the bubbles or financial manias described by Mackay are the South Sea Company bubble of 1711--1720, the Mississippi Company bubble of 1719--1720, and the Dutch tulip mania of the early seventeenth century . According to Mackay, during this bubble, speculators from all walks of life bought and sold tulip bulbs and even futures contracts on them . Allegedly, some tulip bulb varieties briefly became the most expensive objects in the world during 1637 . Mackay's accounts are enlivened by colorful, comedic anecdotes, such as the Parisian hunchback who supposedly profited by renting out his hump as a writing desk during the height of the mania surrounding the Mississippi Company . </P> <P> Two modern researchers, Peter Garber and Anne Goldgar, independently conclude that Mackay greatly exaggerated the scale and effects of the Tulip bubble, and Mike Dash, in his modern popular history of the alleged bubble, notes that he believes the importance and extent of the tulip mania were overstated . </P>

Extraordinary public delusions and the madness of crowds