In her silent galleries are there hung micrographs of the living and the dead, of scenes that we have visited, of incidents in which we have borne a part?
Are these abiding impressions mere signal-marks, like the letters of a book, which impart ideas to the mind?
or are they actual picture-images, inconceivably smaller than those made for us by artists, in which, by the aid of a microscope, we can see, in a space not bigger than a pinhole, a whole family group at a glance?
The phantom images of the retina are not perceptible in the light of the day.

Those that exist in the sensorium in like manner do not attract our attention so long as the sensory organs are in vigorous operation, and occupied in bringing new impressions in.

But, when those organs become weary or dull, or when we experience hours of great anxiety, or are in twilight reveries, or are asleep, the latent apparitions have their vividness increased by the contrast, and obtrude themselves on the mind.

For the same reason they occupy us in the delirium of fevers, and doubtless also in the solemn moments of death.

During a third part of our life, in sleep, we are withdrawn from external influences; hearing and sight and the other senses are inactive, but the never-sleeping Mind, that pensive, that veiled enchantress, in her mysterious retirement, looks over the ambrotypes she has collected--ambrotypes, for they are truly unfading impressions--and, combining them together, as they chance to occur, constructs from them the panorama of a dream.
Nature has thus implanted in the organization of every man means which impressively suggest to him the immortality of the soul and a future life.