"Plain? Plain as a flower in the mud on a dark night. But how do you know I've got an—'envelope'?"
"Every one has. Why, De Roche has actually photographed one, by means of radio-photography."
Grimm lay back in his chair and shouted aloud with laughter.
"Mind you," went on McPherson, laboriously anxious to make clear his point, "they could not see it when they were photographing it."
"No, I should imagine not. Nor the picture after it was taken. But in other respects, I don't doubt it was a splendid likeness."
"Wait, before you try to be funny. Wait till I tell you about it. This 'envelope' or Shadow Self stood a few feet away from the sleeper. It was invisible, of course, to the eye. It was only located by striking the air and watching for the corresponding portion of the sleeper's body to recoil. By pricking a certain part of the Shadow Self with a pin, the cheek of the patient could be made to bleed. It was at that spot that the camera was focussed for fifteen minutes! The result was——"
"A spoiled film."
"No, the profile of a head!" contradicted Dr. McPherson.
Grimm stared at him wonderingly.
"And you actually believe such idiocy?" he demanded.