388 ANNUAL OF SCIENTIFIC DISCOVERY. 



of the total eclipse of July 1800, no appearance of any intra-Mcrcnrial 

 planet was detected. 



Taking, then, into consideration the nnmerons observations that have 

 been made on the sun and in its vicinity by so many astronomers, and with 

 such fine telescopes, M. Liais concludes "that if the motion of the perihelion 

 of Mercury is due to the attraction of matter lying bctAveen the sun and 

 this planet, this matter does not form planets, properly so called, but must 

 be in a state of cosmical dust, and form a part of the solar nebulosity or 

 zodiacal light." 



4. M. Liais's last observation, questioning the existence of a disturbing 

 force requiring for its cause the existence of a planet or planets, merits, 

 doubtless, the attention of astronomers. The motion of the perihelion of 

 Mercury has been deduced from twelve observed passages of this planet. 

 Admitting the time of the planet's entrance upon the sun's disk to be 

 affected with refraction, M. Liais has obtained, by calculation, a motion of 

 the perihelion so much less than that assumed by LeYerrier, that he can 

 account for it by supposing the mass of Venus to be from the tenth to the 

 fifteenth greater than it is supposed to be. By admitting a possible error in 

 the obliquity of the ecliptic of two and one-half seconds, and, consequently, 

 an increase of one-tenth in the mass of Venus, M. Liais asserts that the 

 whole motion in the perihelion of Mercury may be explained; and he fur- 

 ther asserts that, by abandoning the invariability of the mean motions, 

 which supposes a constancy in the masses, of which there is no proof, the 

 position of Mercury may be explained without supposing so great a motion 

 in his perihelion as has been alleged. 



To these remarkable positions assumed by M. Liais no reply has been 

 made by either LeVerrier or Lescarbault. As already stated, however, since 

 the announcement of the discovery the sun has been anxiously observed by 

 astronomers; and the limited area around him in which the planet must be, 

 if he is not upon the sun, has doubtless been explored with equal care by 

 telescopes of high power and processes by which the sun's direct light has 

 been excluded from the tube of the telescope as well as the eye of the ob- 

 server; and yet no planet has been found. This fact would entitle us to 

 conclude that no such planet exists, if its existence had been merely conjec- 

 tured, or if it had been deduced from any of the laws of planetary distance, 

 or even if LeVerrier or Adams had announced it as the probable result of 

 planetary perturbations. If the finest telescopes cannot rediscover a planet 

 that has a visible disk, with a power of three hundred, as used by Liais, 

 within so limited an area as a circle of sixteen degrees, of which the sun is 

 the centre, or rather within a narrow belt of that circle, we should unhesitat- 

 ingly declare that no such planet exists; but the question assumes a very 

 different aspect when it involves moral considerations. If, after the severe 

 scrutiny which the sun and its vicinity will undergo, no planet shall be seen, 

 and if no round black spots distinctly separable from the usual solar spots 

 shall not be seen on the solar disk, we will not dare to assert that it does not 

 exist. We cannot doubt the honesty of M. Lescarbault, and we can hardly 

 believe that he was mistaken. No solar spot, no floating scoria, could main- 

 tain, in its passage over the sun, a circular and uniform shape; and we are 

 confident that no other hypothesis but that of an intra-Mercurial planet can 

 explain the phenomena seen and measured by M. Lescarbault a man of 

 high character, possessing excellent instruments, and in every way compe- 

 tent to use them well, and to describe clearly and correctly the result of his 



