The simultaneous disappearance of Jupiter’s four moons, with some notes upon the laws that govern their motions

Abstract

The four satellites, which accompany the planet Jupiter, are known to disappear when they enter into the planet's shadow, causing eclipses much more frequent than, but in other respects quite analogous with those of the moon. Galileo, who first contemplated those phenomena, at once inferred that observations of this kind might be rendered subservient to the promotion of geographical science. It only required that the course of these satellites should be reduced into tables of sufficient exactness to rectify a multitude of errors in the determination of longitude. Observatory, 8th July, 1867.