There is an amazingly silly proverb which quite mistakenly tells us that "seeing is believing." The most ordinary conjurer at a village entertainment will prove the falsity of this saying. For who has not seen one of these plausible mountebanks put a watch into a top-hat and after clearly smashing it into a thousand pieces with a pestle stir up the disintegrated fragments with a spoon and produce an omelette? Or who is so unacquainted with the affairs of the village schoolroom at Christmas as not to have seen a solid billiard-ball or a lively canary squeezed out of the side of a friend's head? Such phenomena are by no means rare and occur periodically all over England. The observer's eyes have told him that he has seen such things and the verb "to see" is merely a compendious expression to indicate that on the evidence of your eyes such or such a phenomenon has actually occurred. But no one believes that the disintegrated watch has become an omelette though ocular evidence seeing insists that it has. It was a conjuring trick. And this leads me to the consideration of the phenomena on which this whole book is based.