On first viewing an unfamiliar scene many people have, doubtless, experienced the curious sensation of having seen it before. This may have been obviously impossible. It may have been in a part of the world visited for the first time and yet there is a feeling so haunting in some instances as to be distressing—that it is all a repetition of something that has occurred in the indefinite past.
This is a phenomenon so common that various theories have been offered in explanation. The most commonly accepted is that of the psychologist, who tells us that at the instant of the first glance the mind is pre-occupied and that a space of time, which may be infinitely minute and imperceptible, elapses before the intelligence can grasp the meaning of the sensual impression and interpret it into a cognizable fact. In the realm of the subconscious there is no measure of