Manchester Memoirs, Vol. /iv. {igog), No. 1. 7 



23. The Astronomer Royal (Sir George B. Airy) in his 

 historical review of the circumstances connected with the 

 discovery of Neptune says that " if the mathematicians, 

 whose labours I have described, had not adopted Bode's 

 law of distances (a law for which no physical theory of 

 the rudest kind has ever been suggested), they would 

 never have arrived at the elements of the orbit,"* or, in 

 other words, would never have discovered Neptune. 



24. The most probable, as well as the most obvious, 

 cause of the anomalous minus difference in the binary 

 progression of the distance of Neptune is the outermost 

 position of the planet in relation to the other members of 

 the system, with the consequent conjoint attractions of all 

 the planets, acting through every part of their orbits, to 

 contract continuously and permanently his radius vector 

 to the amount shown in the observations. The large 

 amount of this contraction is strong presumptive evidence 

 against the existence of a planetary body beyond the orbit 

 of Neptune. 



25. A further consequence of the outermost position of 

 Neptune is the small amount of the eccentricity of his orbit, 

 0009, or nearly six: times less than the eccentricities of 

 Uranus, Saturn and Jupiter, and, excepting Venus, 0007, 

 is the nearest approach to a circular orbit of any member 

 of the system. 



26. It is not a little remarkable that the inevitable 

 effect of the outermost position of a planet, to contract 

 continuously its radius vector, has never presented itself to 

 Lagrange, Laplace and other writers on celestial mechanics, 

 who have elaborated the doctrine of the absolute stability 

 of the solar system. The conjoint attractions of all the 



*Proc. Roy. Astron. Soc, Nov. 13, 1846, Phil. Mag., (3), vol. 29, 

 pp. 520, 537, 1846. 



