An additional observatory was added in the 1820s, but the smoky skies and train steam over the city at that time made it an unsuitable location for watching the stars.
The observatory was abandoned in the late 1840s.
mnli hypothesis: The observatory was abandoned in the late 1840s. premise: An additional observatory was added in the 1820s, but the smoky skies and train steam over the city at that time made it an unsuitable location for watching the stars.