s, like Shelley's poet,

"Hidden in the light of thought."

So, some say the sun may be dark as another planet; and that the spots
on it are its common earth seen through the gaps in its luminous
atmosphere.

To the world, the alpha and omega of this piece of philosophy were
furnished by the publication of the case of Nicolai, the bookseller of
Berlin. Its details were read before the Academy of Sciences at Berlin,
in 1799. The _substance_ ran thus. Nicolai had had some family troubles
which much annoyed him. Then, on the 21st of February 1791, there stood
before him, at the distance of ten paces, the ghost of his eldest son.
He pointed at it, directing his wife to look. She saw it not, and tried
to convince him that it was an illusion. In a quarter of an hour it
vanished. In the afternoon, at four o'clock, it came again. Nicolai was
alone. He went to his wife's room--the ghost followed him. About six
other apparitions joined the first, and they walked about, among, and
through each other. After some days the apparition of his son stayed
away; but its place was filled with the figures of a number of persons,
some known, some unknown to Nicolai--some of dead, others of living
persons. The known ones were distant acquaintances only. The figures of
none of Nicolai's habitual friends were there. The appearances were
almost always human: exceptionally, a man on horseback, with dogs and
birds would present themselves. The apparitions came mostly after
dinner, at the commencement of digestion. They were just like real
persons; the colouring a thought fainter. The apparitions were equally
distinct whether Nicolai was alone or in society, by day as in the dark,
in his own house or those of others; but in the latter case they were
less frequent, and they very seldom presented themselves in the streets.
During the first eight days they seemed to take very little notice of
each other, but walked about like people at a fair, only here and there
communing with each other. They took no notice of Nicolai, or of his
remarks about them to his wife and physician. No effort of his would
dismiss them, or bring an absent one back. When he shut his eyes, they
sometimes disappeared, sometimes remained; when he opened his eyes, they
were there as before. After a week they became more numerous, and began
to converse. They conversed with each other, and then addressed him.
Their remarks were short and unconnected, but sensible and civil. Hi