A Historical Aside: Meanwhile, the Discovery of Neptune

Ephemerides were published for Uranus in the 1820's. People began noticing serious discrepancies between its predicted and observed positions.
Adams (1843) and Le Verrier (1846) had worked independent positions for an unseen planet perturbing Uranus' orbit.
Adams sent his calculations to the Royal Astronomer, Sir George Airy, but they were never followed up with observations.
Le Verrier had easier telescope access, and on September 23rd, 1846, Neptune was found 1 degree from his predicted position.
This triumph for predictive science was the model from which Lowell was trying to work.