It is by this theory of the duality of the brain, which seems to have many arguments in its favor, and the alternate sleeping and waking of the two sides, that Dr. Wigan seeks to account for the state of double or alternate consciousness above alluded to; and also, for that strange sensation which most people have experienced, of having witnessed a scene, or heard a conversation, at some indefinite period before, or even in some earlier state of existence. He thinks that one half of the brain being in a more active condition than the other, it takes cognizance of the scene first; and that thus the perceptions of the second, when they take place, appear to be a repetition of some former experiences. I confess this theory, as regards this latter phenomenon, is to me eminently unsatisfactory, and it is especially defective in not accounting for one of the most curious particulars connected with it, namely, that on these occasions people not only seem to recognise the circumstances as having been experienced before; but they have, very frequently, an actual foreknowledge of what will be next said or done. Now, the explanation of this mystery, I incline to think, may possibly lie in the hypothesis I have suggested; namely, that in profound, and what appears to us generally to have been dreamless sleep, we are clear-seers. The map of coming events lies open before us, the spirit surveys it; but with the awaking of the sensuous organs, this dream-life, with its aerial excursions, passes away, and we are translated into our other sphere of existence. But, occasionally, some flash of recollection, some ray of light from this visionary world, in which we have been living, breaks in upon our external objective existence, and we recognise the locality, the voice, the very words, as being but a reacting of some foregone scenes of a drama. The faculty of presentiment, of which everybody must have heard instances, seems to have some affinity to the phenomenon last referred to. I am acquainted with a lady, in whom this faculty is in some degree developed, who has evinced it by a consciousness of the moment when a death was taking place in her family, or among her connections, although she does not know who it is that has departed. I have heard of several cases of people hurrying home from a presentiment of fire; and Mr. M—— of Calderwood was once, when absent from home, seized with such an anxiety about his family, that without being able in any way to account for it, he felt himself impelled to fly to them and remove them from the house they were inhabiting; one wing of which fell down immediately afterward. No notion of such a misfortune had ever before occurred to him, nor was there any reason whatever to expect it; the accident originating from some defect in the foundations.