EIGHTH SATELLITE OF SATURN. 99 



the motion of Saturn toward the south was IS" in 4 

 hours, it would plainly have left the point x behind, if it 

 had been a fixed star. The conclusion is inevitable ; x 

 is a satellite hitherto undiscovered. This is explained by 

 its being a very faint object, even in my telescope of 24 

 inches aperture; and it may experience variations of 

 light, which render it invisible in some parts of its orbit. 



" I obtained two other observations of the satellite on 

 the 21st and 22d. In the former case, the elongation to 

 the east of the planet was 3' 54"; and in the latter 3' 27" ; 

 the star followed sensibly the line of the interior 

 satellites." 



Thus it appears that a most important discovery was 

 made independently and almost simultaneously on op- 

 posite sides of the Atlantic but Mr. Bond has an 

 unequivocal priority of two days. This is the first ad- 

 dition to our planetary system made by an American 

 astronomer. The orbit of the new satellite lies between 

 Titan and lapetus, and serves to fill up a large chasm 

 before existing. It is fainter than either of the two 

 interior satellites discovered by Sir William Herschel. 

 Its time of revolution is about 21d. 4h. 20ra. ; its semi- 

 axis at the mean distance of Saturn 214", indicating a 

 real distance of about 940.000 miles, and Messrs. Bond 

 and Lassell have concurred in giving it the name of 

 Hyperion. 



It will be observed that there is still a large gap 

 between Hyperion and lapetus, rendering it not improb- 

 able that other satellites yet remain to be discovered. 



