470 Prof. P. Lowell on 
At the same time measures of the whole ring gave: — 
Mean of 
2 measures. On the right measured from the nearest 
limb, reduced to equat. radii from 
the planet's centre 2*164 
1 measure. On the left measured from the nearest 
limb, reduced to equat. radii from 
the planet's centre 2-145 
4 measures. From W. to E. end visible double 
measures, reduced as above 2-191 
The equatorial radius, also measured, came out : — 
Mean of 
2 measures 9"-245 
Several things are deducible from these measures. First: 
It is evident that the rings could not be followed quite to the 
outer limit of ring A, as that stretches to 2'25 or 2*30 radii 
from the centre of the planet, according to whose measures 
of the system we adopt, while the measured breadth was now 
at most 2'19. This implies that the outer part of ring A has 
less thickness than the rest ; for we cannot refer the effect 
to less breadth of ring there being intersected by the line of 
sight, since the earth was on the opposite side of the ring- 
system from the sun. The average width of the thread of 
light upon which the agglomerations were strung was by 
comparison with the black core of the shadow not over 
80 miles. 
Secondly : The present measures indicate that the rings 
approach the body of the planet closer than they have been 
measured before. 
Thirdly : The measures of the positions of the agglome- 
rations show that Olbers' explanation of them, endorsed by 
Seeliger, fails to account for the appearances. 
Fourthly : These positions point to another explanation of 
some interest. And 
Fifthly : This latter explanation proves also to account for 
the phenomena of the shadow, and incidentally to answer a 
query propounded by Seeliger on previous observations of it. 
To make this clear we will begin by quoting Seeliger upon 
the observations and deductions on the last occasion when the 
rings were presented as now edgewise to the earth. 
" The ring, according to Mr. Barnard, was completely in- 
visible at the end of October, 1891, even in the most powerful 
glass of the Lick Observatory. He caught it for the first 
time on October 30, 1891, l h 7 m G.M.T. As Mr. Oudemans 
could see nothing of the ring on October 29, 17 h 9 m G.M.T. , 
& ~- *"~~ *■■""& 
