In the following Letters I have endeavoured to exhibit in their true light the singular natural phenomena of which old superstition and modern charlatanism in turn availed themselves—to indicate their laws, and to develop their theory." (from the Preface of the book) In 14 letters, British physiologist Herbert Mayo (1796-1852) is giving the reader an overview of popular superstitions of previous times, like vampirism, somnambulism or even ghost sightings, and exposing how in previous times they were treated with fear, ignorance and intolerance, often leading to crime, while he endeavours to give rational explanations for the phenomena with the goal to find treatments and cures for the afflicted. - Summary by Sonia