the Tores of Saturn. 471 
its reappearance falls within the narrow interval between 
these two dates. At that time the earth had an elevation 
above the ring o£ 1° 56'. Mr. Oudemans further remarked 
on the same day: ' a fine dark streak* runs across the equator/ 
and explained this as the projection of the dark ring upon 
Saturn's disk, because it still remained visible after the 
Sun had risen a little over the plane of the ring. Against 
this interpretation there is practically nothing to be said ; 
only it may perhaps be remarked that here might well be the 
work of the bright ring too. For the shadow made by this 
ring does not lie exactly between two planes, and a part of it 
could constantly be found in the shadow of the other ring, 
even after the Sun had risen a little over the plane of the 
ring-system. One has thus the advantage of explaining a 
somewhat greater breadth of the dark streak ; and this is to 
welcomed, as the minor part of the crape ring, as above 
remarked, is almost completely transparent, and therefore 
lets the disk of Saturn behind it be seen and itself does not 
appear quite black." 
" Before the ring begins to be visible, it must disclose itself 
as a dark stripe across Saturn's disk. This was a fact seen 
and drawn by Mr. Barnard. He found on October 22, for 
the breadth of the dark band 0"*51 and for the position of its 
middle point from the north limb (of the planet) 7 ,/, 40; from 
the south one 6"'56. Mr. Barnard asserts that the measured 
breadth entirely agrees with the ephemeris data. I find, 
however, for an elevation of 1° 41' for the earth above the 
plane of the ring, its width to be 0"*16 or 0"*24, according 
as the bright ring alone is considered or the dark ring is in- 
cluded as well. On the contrary, I find very good agreement 
between the observations and the data for the position of the 
dark band of 7 / '*64 and 6"'72 from the north and south limits 
respectively, and of 7 / '*60 and 6"*76 if the dark ring be 
also comprised. The above remarked divergence between ob- 
servation and theory demands explanation, since Mr. Barnard 
on October 29 found an even greater breadth of the dark 
band of 0"-65." 
" From the very interesting notices of Mr. Barnard on the 
appearance of the ring when it became visible on October 29, 
1891 (October 30, 1891 ?, see above), the following points 
deserve prominence. The ring could first be seen at a distance 
of about 2" from the edge of the disk; also the two halves 
on either side were not the same ; and lastly Mr. Barnard 
* Mr. Oudemans here refers to the whole shadow, as appears from 
Barnard's measures of it cited below. Neither he nor Barnard saw its 
Mack core. 
