The bottom, or under surface, which appears to those who view it below, is one even regular plate of adamant, shooting up to the height of about two hundred yards.
In this cave are twenty lamps continually burning, which, from the reflection of the adamant, cast a strong light into every part.
This magnet is sustained by a very strong axle of adamant passing through its middle, upon which it plays, and is poised so exactly that the weakest hand can turn it.
It is hooped round with a hollow cylinder of adamant, four feet yards in diameter, placed horizontally, and supported by eight adamantine feet, each six yards high.
The stone cannot be removed from its place by any force, because the hoop and its feet are one continued piece with that body of adamant which constitutes the bottom of the island.
At the centre of the island there is a chasm about fifty yards in diameter, whence the astronomers descend into a large dome, which is therefore called flandona gagnole, or the astronomer’s cave, situated at the depth of a hundred yards beneath the upper surface of the adamant.
…larger cities, a situation probably chosen at first with a view to prevent such a catastrophe; or if it abound in high spires, or pillars of stone, a sudden fall might endanger the bottom or under surface of the island, which, although it consist, as I have said, of one entire adamant, two hundred yards thick, might happen to crack by too great a shock, or burst by approaching too near the fires from the houses below, as the backs, both of iron and stone, will often do in our chimneys.