448 HISTORY OF PHYSICAL ASTRONOMY. 



employed in searching the sky for it in vain. At last, after many 

 trials, Von Zach and Olbers again found it, the one on the last day of 

 1801, the other on the first day of 1802. Gauss and Burckhardt im- 

 mediately used the new observations in determining the elements of 

 the orbit ; and the former invented a new method for the purpose. 

 Ceres now moves in a path of which the course and inequalities are 

 known, and can no more escape the scrutiny of astronomers. 



The second year of the nineteenth century also produced its planet. 

 This was discovered by Dr. Olbers, a physician of Bremen, while he 

 was searching for Ceres among the stars of the constellation Virgo. 

 He found a star which had a perceptible motion even in the space of 

 two hours. It was soon announced as a new planet, and received from 

 its discoverer the name of Pallas. As in the case of Ceres, Burck- 

 hardt and Gauss employed themselves in calculating its orbit. But- 

 some peculiar difficulties here occurred. Its eccentricity is greater 

 than that of any of the old planets, and the inclination of its orbit to 

 the ecliptic is not less than thirty-five degrees. These circumstances 

 both made its perturbations large, and rendered them difficult to cal- 

 culate. Burckhardt employed the known processes of analysis, but 

 they were found insufficient : and the Imperial Institute (as the French 

 Academy was termed during the reign of Napoleon) proposed the 

 Perturbations of Pallas as a prize-question. 



To these discoveries succeeded others of the same kind. The Ger- 

 man astronomers agreed to examine the whole of the zone in whi ?h 

 Ceres and Pallas move ; in the hope of finding other planets, frag- 

 ments, as Olbers conceived they might possibly be, of one original 

 mass. In the course of this research, Mr. Harding of Lilienthal, on 

 the first of September, 1804, found a new star, which he soon was led 

 to consider as a planet. Gauss and Burckhardt also calculated the ele- 

 ments of this orbit, and the planet was named Juno. 



After this discovery, Olbers sought the sky for additional fragments 

 of his planet with extraordinary perseverance. He conceived that one 

 of two opposite constellations, the Virgin or the Whale, was the place 

 where its separation must have taken place; and where, therefore, all 

 the orbits of all the portions must pass. He resolved to survey, three 

 times a year, all the small stars in these two regions. This under- 

 taking, so curious in its nature, was successful. The 29th of March, 

 1807, he discovered Vesta, which was soon found to be a planet. And 

 to show the manner in which Olbers pursued his labors, we may state 

 that he afterwards published a notification that he had examined the 



