14 Dr. Herschel's Observations on the 
grees past the opposition till towards the inferior conjunction, 
it is not only less bright than the 3d, but hardly, if at all, ex- 
ceeds the 2d, or even the 1st satellite; provided the latter be 
then about its greatest elongation, where its light is least im- 
peded by the brightness of the planet. Upon the whole, the 
alteration seems to amount to what among the fixed stars, and 
with the naked eye, would be called a change from the 5th to 
the 2d, and from the 2d to the 5th magnitude. 
Having thus observed this satellite, for many of its revolu- 
tions round the primary planet, to lose and regain its light re- 
gularly, it is evident that the time of its rotation on its axis 
cannot differ much from that of its revolution round Saturn. I 
think myself sufficiently authorized to make this conclusion, 
notwithstanding it may have happened sometimes that the 
light of the satellite has suffered an occasional change, of short 
duration, from other causes; for the same reason that we 
should certainly allow those who first saw the spots in the sun 
to be in the right to assign the period of its rotation nearly , 
when they perceived that the same spot made several revolu- 
tions, notwithstanding that spot might afterwards vanish. But 
I may go farther, and ascertain upon sufficient grounds, that 
this satellite turns once upon its axis, exactly in the time it 
performs one revolution round its primary planet. This de- 
gree of accuracy is obtained by taking in the observations of 
M. Cassini, which are related in the Memoires de I’Academie 
des Sciences , 1705, page 121 ; where we find it mentioned, that 
“ the 5th satellite of Saturn disappears regularly for about one 
“ half of its revolution, when it is to the east of Saturn.” The 
same memoir contains also a conjecture of this satellite's rota- 
tion upon its axis ; but this surmise is contradicted as prema- 
