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JUPITER WITHOUT HIS SATELLITES. 
By RICHARD A. PROCTOR, B.A., F.R.A.S., 
Author of u Saturn and its System fyc. 
O N August 21, of the present year, the planet Jupiter will 
appear in telescopes of moderate power, to be unaccom- 
panied for the space of one hour and three quarters by the 
satellites usually seen in attendance upon him . This phenom enon 
has been so seldom observed that considerable interest is attached 
to it. Molyneux on November 12, 1681 (0. S.), Sir W. Herschel 
on May 23, 1802, Wallis on April 15, 1826, and Dawes and 
Griesbach on September 27, 1843, are, I believe, the only 
observers who have hitherto seen Jupiter without his comites. It 
cannot be doubted, however, that if the weather be favourable, 
the number of observers who have seen the phenomenon, wfill be 
very largely increased before midnight August 21. It will not 
be wholly as a matter of curiosity that observations will be made 
on that night. The record of phenomena presented by Jupiter’s 
satellites is a regular part of “ observatory work,” and is very 
necessary for the improvement of the theory of their motions, — 
an important astronomical subject A special value is attached 
to the record of phenomena separated by a small interval of time, 
so that the observations made are fairly comparable inter se, free 
from the errors arising from variations in clock rates, instru- 
mental changes, and the like. Now on the evening of August 21 
there will be eight phenomena visible within six hours, — viz. the 
disappearances, and reappearances of four satellites. To ob- 
servers suitably armed there will, indeed, be no less than thirteen 
phenomena visible within the above-named interval ; since of 
the entrances and exits of the shadows of three satellites, six 
phenomena in all, five will be observable with good telescopes. 
Six months ago, I had occasion to treat of Mars, nearly the 
lowest in the scale of planetary magnitude, and interesting as 
presenting a charming miniature of our own earth. The con- 
trast between this orb, and the planet we are now to consider 
is marked indeed. Jupiter stands at the other end of the scale 
of planetary magnitude. He surpasses our earth more than 
1400 times in volume. Saturn alone can be compared with him 
