capable of anything.

“Yes,” said the old man, enjoying his bewilderment. “My ghosts may be different from those you have in mind. If you have followed the recent developments in psychology you probably know that there are ghosts attached to the living, whatever the case may be in regard to the dead.”

“No, I never heard that.”

“Not in those words. ‘Ghosts’ is not a term used by the scientist. It involves a medieval superstition. But I am interested in things more than in words, and I am not afraid to say that we have been rediscovering ghosts.”

“Uncle, don’t talk enigmas—or nonsense,” remonstrated Una.

“I confess, sir, I don’t follow you,” added David.

“Did you ever feel that you had lost yourself?” asked Leighton abruptly.

“I don’t understand.”

“If you forget a thing, you lose just that much of yourself, don’t you? When you sleep, you enter a world of dreams. In that world you think, speak, go through a set of vivid experiences. Awake, you are aware that you have had these vivid experiences—and yet, you can’t possibly remember them. You are dimly conscious that you were in another world and that while there you thought, suffered, rejoiced, much in the same way that you do here. At times you have a vague feeling that you have undergone some important crisis in your dream-existence, or you wake up with the sensation of having reached some high peak of happiness. But you cannot recall the details, or even the general outlines, of what has happened. Not a scene of this dreamland, of which you are an occasional inhabitant, can you picture to your waking thought; nor does your waking memory hold the visage, or even the name, of one of your dream-associates.”

“All this has to do with dreams,” objected David. “It is admittedly unreal.”

“Don’t rely too much on old definitions. A part of you that sleeps now does experience this dream-life and finds it real. The trouble is, this dream part of you forgets; it is unable to report to the waking personality what it has seen.

“But it is not only in sleep that this dream-personality takes the place of that which we call the real self. The opium-eater inhabits a world, opened to him by his drug, and closed, even to his memory, when the effects of that drug wear off. Then, there is that curious phase of dipsomania in which the victim, apparently possessed of all his faculties, goes through actual experiences—travels, talks with people, transacts business—and when he recovers from his fit of intoxication finds it impossible to remember a single circumstance of the many known to him while under the sway of alcohol. The phenomena of hypnotism give instances of similar independent mental divisions in a single human personality. All this is the familiar material of modern psychology, out of which the scientists build strange and varied theories. I call these divided, or lost, personalities ‘ghosts.’”

“Ghosts of the living, not of the dead.”

“More uncanny than the old-fashioned kind,” mused Una. “Fancy meeting one’s own ghost!”

“Cases of such meetings are on record; Shelley’s, for instance,” said Leighton drily.

“The thing is strange and worth investigating. But,” added David laughingly, “I am not an investigator.”

“It is fascinating,” declared Una emphatically. “Tell us more about it, Uncle Harold. You spoke of an experiment——”

“The experiment, by all means,” said David. “Just what is it?”

“Trapping a ghost,” was the laconic answer.

“And if you succeed in trapping it——?”

“Ah, then—science generally leaves its ghosts to take care of themselves. It’s a good rule.”

“You say you are going to trap a ghost: you don’t really mean that,” protested Una.

“Remember, there are two kinds of ghosts. As a scientist I am not interested in the ghosts of the dead. If they exist outside of fairy tales and theology let some one else hunt them. But I am interested in the other and more profitable kind—the ghosts of the living.”

“I don’t understand,” said David.

“It needs explanation. Remember what I said as to the phenomena presented by the dreamer, the hypnotic subject, the dipsomaniac, the narcomaniac. In each of these cases one human mind seems capable of division into two independent halves. And each half seems to forget, or to be ignorant of the doings of its mate. Now, I am hunting for this Ghost of the Forgotten.”

“Sounds romantic,” remarked David. “According to your theory, don’t you need a hypnotized subject—or at least a dipsomaniac—for your experiment?”

“No. The Ghost of the Forgotten lurks in all of us. The man or woman in whom this Ghost is not to be found is exceptional. I doubt if such a being exists—a being whose Book of the Past is as clear, as legible, as his Book of the Present.”

“But, your experiment, Uncle,” demanded Una; “show it to us.”

“I need help for a satisfactory trial. An experiment isn’t a picture, or a book, you know. It needs a victim of some kind. What do you say, David?” he asked, turning abruptly to him.

“You want me for the victim?” laughed David. “I’m ready. Feel just like my namesake before he tackled that husky Philistine. Tell me what I’m to do.”

They were standing at the fireplace, Una with one arm through her lover’s, the other resting on her uncle’s shoulder. A scarcely perceptible frown clouded Leighton’s features before he accepted David’s offer.

“I merely want you to answer some questions,” he said finally. “You will think them trivial; but I want you to answer them under unusual conditions. Let me show you my latest prize and explain things.”

Leighton strode to the center of the room and thence down to that end of it where the tools of his laboratory were kept. David and Una followed, enjoying the momentary relief from the scrutiny of the old savant, who was now, apparently, engrossed in his scientific apparatus. There was not much of the latter in sight, and to the novice unfamiliar with the interior of a physicist’s laboratory, and who carries away a confused impression of glass and metal jars, tubes, coils of wire, electric batteries, revolving discs, and all the nameless paraphernalia of such a place, the appointments of Harold Leighton’s workshop would seem simple enough. Yet, the machine before which Leighton paused comprised one of the newest discoveries in this branch of science. Its sensational purpose was to measure and probe the mind through the purely physical operations of the body.

What appeared to be, at first glance, an ordinary galvanometer stood by itself on a table. Its polished brass frame, its flawless glass cylinder enclosing the coils of wire, recording discs and needle, suggested nothing more than the instrument, familiar to the physicist, by which an electric current is measured and tested. Connected with this galvanometer, however, was a curious contrivance consisting of a mirror, over the spotless surface of which, when the machine was in operation, a ray of light, projected from an electrified metal index, or finger, moved back and forth. The exact course of this ray of light, the twists and turns made by it in traversing the mirror, was transferred by an automatic pencil to a sheet of paper carried on a revolving cylinder. This paper thus became a permanent record of whatever experiment had been attempted.

That the subjects investigated by this unique galvanometer were human and not inanimate was indicated by two electrodes, attached by wires hanging from the machine, intended to be grasped by the hands of a