T.C. Lethbridge-who was Keeper of Anglo-Saxon Antiquities at Cambridge-stumbled on the "psychometric" theory as a result of his own observations. When he saw the "ghost" of the man in a hunting kit, he was at first inclined to wonder whether it had been purely a mental picture, perhaps "pickedup" from somebody else's mind. Perhaps the huntsman had been a former occupant of the rooms, and was sitting in his armchair at home sipping a whisky as he thought about the good old days at Cambridge; and perhaps somehow the image had got itself transferred into Lethbridge's mind...

But other experiences led him to revise this notion. One day, after he had retired to Devon, Lethbridge and his wife Mina went to collect seaweed from Ladram beach. It was a dull, damp day, ad as they walked on to the beach near a stream that ran down the cliff, both suddenly experienced a profound depression. Lethbridge noticed that this vanished as soon as he stepped a few feet away from the stream. His wife, Mina, went to the cliff top to make a sketch, and suddenly had the odd feeling that someone was urging her to jump. (Again, Lethbridge was inclined to think that she could have been picking up someone's thoughts-perhaps someone had stood on that spot, contemplating suicide, then had a change of mind and gone home-but later investigation revealed that a man had committed suicide from exactly that spot).

Thinking about it all later, Lethbridge reflected that dampness can cause radio transmitters to short-circuit. Could it have been the dampness on the beach that was somehow responsible for the feeling of depression? He had also been struck by the fact that it seemed to end so abruptly, as if it formed a kind of invisible wall. He had noticed the same kind of thing around the cottage of an old woman reputed to be a witch-who had died under circumstances suggesting murder. There was the same "nasty feeling" around the place just after her death, and he had noticed that he could step in and out of it, as if it ended quite sharply. Could it, Lethbridge wondered, be some kind of "field," like the field that surrounds a magnet?

Lethbridge was also an excellent dowser, and it struck him that the "nasty feeling" on the beach (he used the term "ghoul" to describe it) had been around the stream. This led him to the theory that the "field" of water can "tape record" strong emotions, and that people who can dowse are probably able to "pick up" these recordings. In short, a water-diviner would be far more likely to see a ghost than most people.

This, then, was Lethbridge's theory about "ghosts" and "ghouls," which he developed in a number of books written in the last ten years of his life (he died in 1972). It is a natural and logical extension of Buchanan's "psychometry" and of Lodge's theory about "recordings." But Lethbridge has also placed it on a more scientific basis by suggesting that what does the "recording" is some kind of magnetic field associated with water. The principle sounds very much like that of a tape recorder, where a magnetic field "imprints" the sounds on an iron-oxide tape. In Lethbridge's theory, the magnetic field of water records emotions and prints them on its surroundings-in the case of the "old witch," on the walls of her damp cottage.