CHAPTER XIV 



SCIENTIFIC PREDICTION THE DISCOVERY OF 



NEPTUNE 



UNDER this heading we have to consider a single 

 illustration the prediction, and the discovery, in 

 1846, of the planet Neptune. This event roused 

 great enthusiasm among scientists as well as in the 

 popular mind, afforded proof of the reliability of the 

 Newtonian hypothesis, and demonstrated the preci- 

 sion to which the calculation of celestial motions had 

 attained. Scientific law appeared not merely as a 

 formulation and explanation of observed phenom- 

 ena but as a means for the discovery of new truths. 

 "Would it not be admirable," wrote Valz to Arago 

 in 1835, "to arrive thus at a knowledge of the ex- 

 istence of a body which cannot be perceived ? ' 



The prediction and discovery of Neptune, to which 

 many minds contributed, and which has been de- 

 scribed with a show of justice as a movement of the 

 times, arose from the previous discovery of the planet 

 Uranus by Sir William Herschel in 1781. After 

 that event Bode suggested that it was possible other 

 astronomers had observed Uranus before, without 

 recognizing it as a planet. By a study of the star 

 catalogues this conjecture was soon verified. It was 

 found that Flamsteed had made, in 1690, the first 

 observation of the heavenly body now called Uranus. 

 Ultimately it was shown that there were at least 

 seventeen similar observations prior to 1781. 



