One study occasionally illustrates another. In examining the history of
the Earl Marischal, who was exiled after the rising of 1715, I found, in
a letter of a correspondent of d'Alembert, that the Earl met a form of
the fire-walk in Spain. There then existed in the Peninsula a hereditary
class of men who, by dint of 'charms' permitted by the Inquisition, could
enter fire unharmed. The Earl Marischal said that he would believe in
their powers if he were allowed first to light the fire, and then to look
on. But the fire-walkers would not gratify him, as not knowing what kind
of fire a heretic might kindle.