ASTRONOMY OF THE NINETEENTH CENTURY. 425 



A controversy arose between the English and French astronomers 

 as to the right of Adams to participate in the honour of this memor- 

 able discovery. It will be unprofitable to reproduce here any of the 

 contentions on either side. Suffice it to say that Le Verrier's results 

 \vere indisputably first made public, but Airy clearly proved tiiat Adams 

 had completed his calculations eight months before Le Verrier had 

 announced his results to the French Academy. It was only when 

 Airy perused the memoir of Le Verrier's communication that he recog- 

 nized the importance of Adams' communication by the coincidence 

 between his results and those of the French astronomer. Airy imme- 

 diately requested Challis of Cambridge to search for the planet in the 

 region indicated. Challis had not 

 the advantage of the possession 

 of the Berlin map of the stars for 

 this region, but commenced a 

 systematic search on July nth, 

 1846. It was, however, not until 

 the 2 Qth of September that the 

 planetary nature of an object 

 which had been observed as a star 

 on the 4th and 1 2th of August was 

 made out. The British astrono- 

 mers were therefore a few days 

 later than the German in recog- 

 nizing the new planet; upon which 

 it was agreed, after some discus- 

 sion, to confer the name of Nep- 

 tune. 



The data for the deduction were 

 deviations between the observed 

 and calculated places of Uranus, 

 which scarcely exceeded one mi- 

 nute of a degree. Bode's law (page 418) would serve to fix at least ap- 

 proximately the distance of the supposed planet from the sun ; but the 

 estimation of the mass and position of the unknown planet from the 

 perturbations of Uranus requires methods of profound mathematical 

 analysis and laborious calculations, into the details of which it would 

 here be impossible to enter. It will readily be understood that the- 

 elements of Neptune, as determined from actual observations, could 

 not be expected to conform exactly to those calculated a priori by 

 Adams and Le Verrier. But the observed position of the planet when 

 discovered did not differ 2-*- from that indicated by Adams, while 

 Le Verrier's determination was within i of the truth. 



The diagram, Fig, 190, shows the position of Uranus and of Neptune 

 in their orbits at certain epochs between the time of the discovery of 

 Uranus and that of Neptune. The dotted lines indicate the direction 



FIG. 189. LE VERRIER. 



