AMKnNoMK'AL i'HKNOMENA AND PROGRESS. 



69 



hematic*) kill and power, and on the other 



d hard workdevoted to tin- farther- 



anoe of utn>noinie:il ^ience. Tho " Memoir "ii the 



utaiiis the successful development 



..I i.lru, nii-1 ouiiiiot hut be regarded 



! in advance in the method of the vmi- 



(ements and in theoretical dynamics gen- 



>-ts ol' planetary talilew arc works 



of immense lalior, embodying results only attuin- 



i-*e of such labor under the guid- 



; profound mathematical skill and which are 



m tin- present state of astronomy. 1 trust 



tlint. imperfectly us my task is accomplished, I shall 



ii that we have done well in the 



i of our medal. 



The President then, delivering the medal to 

 tin- foreign secretary, addressed him in the fol- 

 lowing terms: 



MK. HCOOINS: I request that you will have the 

 goodness to transmit to Prof. Newcomb this med- 

 al , as an expression of the opinion of the Society 

 of the excellence and importance of what he has 

 accomplished ; and to assure him at the same time 

 of our best wishes for his health and happiness, and 

 for the long and successful continuation of his career 

 as a worker in our science. 



The Planetary Researches of Leverrier . The 

 Comptes Hendus of December 21, 1874, con- 

 tains an interesting account of Leverrier's re- 

 searches on the theories of the eight principal 

 planets, Mercury, Venus, the Earth, Mars, Ju- 

 piter, Saturn, Uranus, and Neptune. When 

 those investigations were commenced, more 

 than thirty years since, none of the tables in- 

 tended to represent the planetary motions ac- 

 corded rigorously with the observations. To 

 discover the unknown causes of these system- 

 atic errors was the principal object of Lever- 

 rier's researches. His theory of Uranus was 

 published in 1846, and led to the discovery of 

 Neptune. This work has been recently re- 

 vised and extended, and the final results were 

 communicated to the Academy of Sciences on 

 the 15th of November, 1874. The theory of 

 Neptune was given in December ; those of 

 Jupiter and Saturn had been previously pre- 

 sented. 



In the case of Mercury M. Leverrier has 

 shown that all the anomalies are included un- 

 der a simple law, and that it "is sufficient to 

 increase the motion of perihelion by thirty-one 

 seconds in the century, to bring every thing 

 into order. The displacement of the perihelion 

 thus acquires in the planetary theories an ex- 

 ceptional importance. It is the surest index, 

 when it has to be increased, of the existence 

 of cosmic matter as yet unknown, and circu- 

 lating, like other bodies, round the sun. The 

 is very clear. There exists in the 



neighborhood of Mercury, doubtless between 

 the planet and the sun, a matter as yet unknown. 

 Does it consist in one or more small planets, or 

 in more minute asteroids, or even in cosmic 

 dust ? The theory tells us nothing on this point. 

 On numerous occasions trustworthy observers 

 have declared that they have witnessed the 

 passage of a small planet over the sun, but 

 nothing has been established on the subject. 1 ' 



M. Leverrier continues : " The discussion of 

 the observations of the sun led us at once to 

 an important result connected with the great 

 <|iicstion which agitate* at this moment the 

 scientific world, a result which surprised us 

 ourselves, so great was the false confidence 

 inspired by the determination of the parallax 

 of the sun deduced by the Director of the Ber- 

 lin Observatory from the transits of Venus in 

 17'>1 and 1769. I arrived at the conclusion 

 that the parallax of the sun, then estimated at 

 8. "67, should be increased by the twenty-fifth 

 part of its value. 



" Soon afterward the comparison of the the- 

 ory of Venus with the observations led to the 

 same result, the necessity of augmenting by 

 ;'- the parallax of the sun. 



" Again, the theory of Mars led in its turn to 

 an equally precise conclusion. It was estab- 

 lished that it was impossible to satisfy the to- 

 tality of the observations of Mars except by 

 increasing the motion of its perihelion by about 

 one-eighth. 



" This was the reproduction of the same fact 

 as for Mercury, and the consequence to be de- 

 rived was the same, viz., that the planet Mars 

 must be subjected to the action of a quantity 

 of matter as yet neglected, and which had to 

 be estimated at about one-eighth of the mass 

 of the earth. 



"But then two hypotheses were possible: 

 either the hitherto neglected matter resided in 

 the totality of the ring of the small planets, or 

 else it had to be added to the earth itself. In 

 the second case, and as a consequence, the 

 parallax of the sun had to be increased by 

 about one twenty-fourth part of its received 

 value ; that is to say, we are led to the result 

 already obtained from the theories of the sun 

 and Venus. 



"Jupiter and Saturn have given rise to a 

 theoretical work, the extent of which has been 

 considerable, on account of the very large 

 mutual perturbations of the two planets. The 

 comparison of the theory of Jupiter with the 

 observations has presented, after suitable mod- 

 ifications of the elements, a complete accord- 

 ance." 



Recent Changes in the Form and Position of 

 Nebula. The Monthly Notices of the Royal 

 Astronomical Society for December, 1874, con- 

 tains a letter from R. J. Ellery, Esq., Director 

 of the Melbourne Observatory, in which he 

 states that he is engaged in a systematic series 

 of observations of Sir John Herschel's figured 

 nebula?. Many of these objects appear to have 

 greatly changed since Herschel's drawings were 

 made at the Cape of Good Hope, between 1834 

 and 1888. These changes are found, according 

 to the observer, not only in the form and char- 

 acter of the nebulae, but also in their position 

 with respect to the adjacent fixed stars as fig- 

 ured by Herschel. Whether such transforma- 

 tions are real, or merely apparent, can only be 

 decided by further observations. 





