Cycles........................

      And in so far as the apparent prosperity is caused by an unusual plentifulness of loanable capital and a consequent rise in prices, that prosperity is not only liable to reaction, but certain to be exposed to reaction.  The same causes which generate this prosperity will, after they have been acting a little longer, generate an equivalent adversity.

-Walter Bagehot, Lombard Street: A Description of the Money Market (1873)