120 Scie?itific Intelligence. 



has been influenced by the action of Neptune only from 1812 to 1842, 



•that is, during only thirty years. 



" It is then during these 30 years only that I have been able to deter- 

 mine directly the position of Neptune: and yet the deviation from my 

 theory is only 3°7 in 1812, at the time when the action of Neptune, 

 which then only commences, was not yet clearly determined. Then, 

 in proportion as this action develops itself, the precision of my indi- 

 cations increases ; and in 1842, at length, when I have at my disposal 

 all the action of the planet, I am mistaken by no more than a fifth of 

 a degree only — that is, by an 1,800th part of the circumference — in 

 predicting the direction in which Neptune should be seen. 



" Thus, far from reproaching my theory with having made the trifling 

 error of 4°0 in 1807 and of 6° 6 in 1797, it should rather be asked, 

 how it could give with such precision the position of Neptune at an 

 epoch when it did not act upon Uranus? In fact, this is only obtained 

 by prolonging arbitrarily the curve which I had obtained from 1812 to 

 1842 ; a prolongation with which my object had nothing to do (qui ripest 

 pas de monfait) and which is not legitimate when pushed too far. Du- 

 ring these thirty years Neptune has performed only a sixth part of its 

 orbit ; an ellipse is very ill determined by an arc including only a sixth 

 part of its extent. 



"During the whole of the last century, from 1700 to 1812, Neptune 

 has in nowise acted upon Uranus. It has had less influence on it than 

 on Saturn, — which it does not sensibly disturb. When I am required 

 to say, by my theory, where Neptune was in the middle or at the com- 

 mencement of the last century, I repeat it, a miracle is demanded of me. 



"I have then the right to say — It is false that I have committed an 

 enormous error in the longitude at every other epoch but that of Galle's 

 discovery or of a few years before and after. During the whole period 

 that Neptune has acted upon Uranus my theory has not deviated from 

 that deduced from direct observations by more than ^ T of the circum- 

 ference. And now it is said that the discovery made by Galle is a for- 

 tuitous accident ! Really, then, planets of twice the size of Uranus and 

 yet unknown, although shining like stars of the seventh magnitude, are 

 scattered in such numbers over the heavens that there is nothing sur- 

 prising if, on pointing by chance to any spot in the firmament there 

 should be great probability of finding one ! And it is, no doubt, on ac- 

 count of their numbers, and because there would be no merit in dis- 

 covering them, that our observers disdain to do so. 





Secondly. — Is it true that there are enormous errors respecting the 

 distance from the Sun ? NO; this is false. Figures have their elo- 

 quence. Here are, according to my plate, the distances from the Sun 

 in the two orbits for the thirty years during which Neptune has acted 

 upon Uranus. 



Distance* in the pre- In Walker's orbit after 



dieted orbit. the discovery. 



In 1812 32-7 304 



1822 33-3 303 



1832 326 302 



1842 328 301 



How is the difference of the two theories to be estimated ? In refer- 



