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XLIV. The Tores of Saturn. By Percival Lowell *. 
ON June 19th (1907) a new phenomenon disclosed itself 
in the Saturnian ring-system. On the morning of that 
day, the planet being so placed at the time as to present its 
rings almost edgewise to the earth, a curious detail was ob- 
served at Flagstaff in the shadow which then banded the 
planet's equator. This equatorial shading, which was in 
truth the shadow of the rings upon the ball, seemed almost 
to belie its function because of the lack of density it offered to 
the eye. Far from being dark, it was only moderately dusky, 
and furthermore presented when first looked at a tripartite 
appearance. On more careful scrutiny, its lack of homo- 
geneity proved to be due to a narrow black line that threaded 
it medially throughout its length, the black core being perhaps 
one-fourth as wide as the less dense background upon w r hich 
it stood. At the same time the rings themselves could with 
attention be made out as the finest knife-edge of light cutting 
the blue of space on either side the planet's disk. As the 
sun was at that moment 32 7 north of the plane of the ring- 
system, while the earth was 2° 16' south of it, the two were 
on opposite sides of the system, which fact combined with its 
then visibility shows that the rings are never wholly lost in 
the Flagstaff glass. 
The planet was not looked at again at Flagstaff until 
October 31j other work occupying the observatory in the 
meantime. In November, however, it was critically studied.. 
The dusky band was evident as in June and the black line 
made core to it as before, being plainly perceptible to all 
the observers. On the 12th and 13th of the month I mea- 
sured both with the micrometer, the measures on the latter 
date being the more numerous and exact ; for the band was 
then measured between the threads, outside them and from 
centre to centre of the same, while the thread-like core was 
estimated in terms of the thread itself. The mean of the 
measures with the suitable corrections applied gave ; — 
for the whole shadow 0"*46 
and for its black core 0"'10 
The band was tinged a faint cherry-red (Nov. 5) ; rather 
more strongly so than the planet's own belts which could be 
seen both north and south of it. The black medial line in 
the midst of it was by no means even. It both undulated 
slightly and showed irregularities of outline, one black bead 
* Communicated by the Author, 
