The principle of plural marriage was revealed to the Mormons amid much secrecy. Dark clouds hovered over the church in the early 1840s, after rumors spread that its founder, Joseph Smith, had taken up the practice of polygamy. While denying the charge in public, by 1843 Smith had shared a revelation with his closest disciples.

The emotions triggered by fiction are very real. When Charles Dickens wrote about the death of Little Nell in the 1840s, people wept - and I'm sure that the death of characters in J.K. Rowling's 'Harry Potter' series led to similar tears.

Bulls don't read. Bears read financial history. As markets fall to bits the bears dust off the Dutch tulip mania of 1637 the Banque Royale of 1719-20 the railway speculation of the 1840s the great crash of 1929.