Laputians were expert astronomers. Demonstrate.

Gulliver finds that, "Most of them, and especially those who deal in the astronomical part, have great faith in judicial astrology, although they are ashamed to own it publicly....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. In this cave are twenty lamps continually burning, which, from the reflection of the adamant, cast a strong light into every part. The place is stored with great variety of sextants, quadrants, telescopes, astrolabes, and other astronomical instruments.