JOURNAL AND PROCEEDINGS. 79 
would describe around him simple elliptical orbits ; but they act on 
each other as well as on the central star, hence from these various 
attractions perturbations result. 
For many centuries past astronomers have computed in advance 
tables of the positions of the stars in the sky, in order to know 
exactly where they could be found and to observe them according 
to the interest presented by their position in their orbits, and also for 
the benefit of navigators. Bouvard, a Paris astronomer, calculated 
in 1820 the tables of Jupiter, Saturn and Uranus, and ascertained 
that his computations agreed exactly with his observation with Jupi- 
ter and Saturn, but not so with Uranus, and for twenty years these 
discrepancies puzzled all astronomers. Bouvard, Madler, Bassel, 
Valz, Arago, etc., expressed the opinion that these discrepancies 
were due to attraction from some planet not yet discovered. * How- 
ever, mathematical calculation went on, and observations of Uranus 
carefully taken. In 1830 the difference of calculation and observa- 
tion increased to 20 seconds, in 1840 to go seconds, in 1844 to 120 
seconds, in 1846 to 128 seconds. ‘To men of the world this would 
have been nothing, as two stars thus separated would require keen 
eyesight to distinguish them as two. But to a man of the skies 
nothing is too small to escape notice, hence such a difference was 
a veritable cause of insomnia. The problem was the topic of the 
day, and Arago, always in the vanguard of progress, advised a young 
man skilful in mathematics—Le Verrier, of France—to undertake 
the problem. After a careful review of the tables of Bouvard, and 
making several corrections, boldly announced the hypothesis of a 
planet beyond Uranus, acting in a continuous manner upon it and 
changing his motion, and on 31st of August, 1846, he announced to 
the Academy of Sciences that a new planet should be found at lati- 
tude 326. On September 18th he wrote to Dr. Gale, of the Berlin 
observatory, telling him that a planet should be observed there, 
and requesting him to look for the planet. Dr. Gale got the letter 
on the 23rd, and it being a clear night he pointed the telescope to 
the position in the sky, and lo! an unknown star appeared, and 
which with increased eye power showed a perceptible disc ; and thus 
far, far away, Neptune was discovered. I should not omit the fact 
that a Mr. Adams in England was at the same time making calcula- 
tions, and leaped to the same conclusion. He wrote the result of 
