82 HISTORY OF ASTRONOMY. 



of known facts is small, they may all frequently be ex- 

 plained by different and conflicting theories. As the 

 number of known facts increases, some of them will 

 probably be found inconsistent with one or the other of 

 the theories, until at last we reach a fact the true experi- 

 mentum crucis which is inconsistent with every theory 

 but one. Thus the true philosopher, instead of regarding 

 the rapidly increasing number of asteroids with indiffer- 

 ence, will watch each new discovery with growing inter- 

 est, in the hope that it may furnish the key to the true 

 theory of the solar system. 



The following table exhibits a summary of the prin- 

 cipal elements of forty asteroids. Column first shows 

 the number of each planet in the order of its dis- 

 covery ; column second the name of the planet ; column 

 third shows the average distance from the sun (the dis- 

 tance of the earth from the sun being taken as unity) ; 

 column fourth shows the number of days required to 

 make one revolution about the sun ; column fifth shows 

 the eccentricity of the orbit, or the quantity by which it 

 departs from the form of a circle ; column sixth shows 

 the number of degrees by which the plane of the orbit is 

 inclined to the orbit of the earth ; column seventh shows 

 the position of the line in which the plane of the orbit 

 intersects the orbit of the earth; and the last column 

 shows the position of that point of the planet's orbit 

 which is nearest the sun. 



The existence of forty planets revolving round the sun 

 at distances closely allied to each other, and differing 



