6 
Dr. Herschei/s Observations on 
see the open heavens through the vacancy between them ; and 
as in my former paper I have given the revolution of the ring, 
which was then supposed to be all in one united mass, it will 
be necessary to examine, whether both rings partake in the 
same revolution, or to which the period which has been as- 
signed belongs? 
To decide this point, we must recur to the observations of 
the spots by which the rotation of the ring was determined. 
The spot called u,* for instance, which has been observed to 
revolve with great regularity through upwards of 300 periods, 
between the 28th of July and the 24th of December, 1789, was 
certainly situated pretty near the outer edge. The spot 1 Q, as 
may be gathered from the observation of the 16th of Septem- 
ber, and 25th of December, was most likely on the very edge 
itself ; nor could the spot $ be far from it. This, without con- 
sidering the situation of y and e, is quite sufficient to determine 
us to assign the period we have given to belong to the large, 
thin and narrow, outward ring. 
The spots y and e were probably at some distance from the 
outward edge of the outer ring ; but this distance might pos- 
sibly not exceed that of the inside edge of the same ring. We 
may however admit them to have adhered to the inner ring, 
whose rotation is perhaps not very different from that of the 
outer one ; or we may examine whether these two spots may 
not perhaps agree to some other supposed revolution of the 
inner ring ; but then the observations that are given of them will 
hardly be sufficient for establishing the time of that ring's ro- 
tation with accuracy, though they undoubtedly must amount 
to a proof that it also revolves with great volocity on its axis. 
* See Phil. Trans. Vol. LXXX. page 481. 
I 
