_The second Source._--A second source, if not of our dreams themselves, at least of the peculiar shape and character which they assume, is to be found in our previous thoughts, and prevalent mental occupations and dispositions. We fall asleep, and mental action goes on much as before, in whatever direction and channel it had already received an impulse. Whatever has made the deepest impression on us through the day, has longest or most intently occupied us, _repeats_ itself the moment we lose our consciousness of surrounding objects. The mind goes on with the new and strange spectacle, or with the unfinished problem, and unsolved intricate study of the day or of the night hour; and not seldom is the train of thought resumed and pursued to some purpose. On waking in the morning, we find little difficulty in completing a demonstration or solving a difficulty which had appeared insurmountable when we left it the previous night. Now the truth is, we did not leave it the previous night. It occupied us in our sleep. The brain was busy with it, it may be, all the night. It is solved in the morning, not because the mind is fresher then, but because it has been at work upon it through the night. Sometimes we are conscious of this on waking, and can dimly recall the severe continuous mental toil which went on while we slept. Usually, I suppose, we have no consciousness of it, and our only evidence of it is the well-known law and habit of the mind, to run in its worn and latest channels, together with the often observed fact that the difficulty previously felt is, somehow, strangely solved. _Further Illustration of the same Principle._--Condorcet is not the only mathematician who has received, in sleep, suggestions which led to the right solution of a problem that he had been obliged to leave unfinished on retiring for the night; nor is Franklin the only statesman who has, in dreams, reached a satisfactory conclusion respecting some intricate political movement. However this may be, there can be no reasonable doubt that our previous mental occupation, our prevalent state and disposition of mind, our habits of thought and habits of feeling, determine and shape the complexion of our dreams. They have a _subjective_ connection, are by no means so disconnected with us and our real history, so much a matter of hap-hazard, as one may suppose. It was not without reason that President Edwards took notice of his dreams as affording an index of the state of his heart, and his real native propensities. They are the vane that shows which way the mind is set. Who will say that the dreams of Lady Macbeth, those dreams of a guilty conscience, are not among the most truthful of the portraitures of the great master dramatist?