10 
NATURE 
[Wov. 3, 1881 
The red spot was suspected to consist of two confluent 
masses, as well as to be somewhat inclined to the neigh- 
bouring belt ; but the former idea, at least, not being 
confirmed by other observers, was probably owing to the 
inferior atmospheric conditions, which did not admit of a 
power much above too. The central girdle consisted as 
usual of three divisions: the N. broadest and darkest, 
and of a cinnamon hue ; the equatorial zone pale grey, 
with very feeble transverse interruptions, an indistinct 
continuation of the “portholes’? so conspicuous some 
years previous; the S. band grey also, but deeper in 
tone. The N. hemisphere, beyond a bright region, had 
many faint grey stripes : towards the opposite pole was a 
feeble brownish shading; so that the colouring of the 
disk as a whole was, in heraldic language, “ counter- 
changed.’’ On other occasions very singular tints have 
been noted by eminent observers—yellovw, full blue, and 
crimson; and the subject well deserves study, even 
though, as seems likely, that study should lead to little 
of a satisfactory nature. 
Then there are other markings to be investigated on 
that great disk, both luminous and dusky, and that in 
another aspect, with a view to the determination of rota- 
tion ; for, strange to say, it is found that some small dark 
specks travel more rapidly than other bright ones, and 
that the red spot moves slowest of all. And thus it is 
that the uncertainty in the axial velocity of that vast 
globe, first noticed by Cassini more than two centuries 
ago, is almost as far from being removed as ever; and, 
on the whole, one is tempted to question whether, after 
all, we have a single accurate idea, excepting that 
of mutability, concerning that enormous surface; and 
whether, if we could be transported there, we should not 
be surprised at the baselessness of all our conjectures. 
Certainly it may be said as to Jupiter, and not as to 
Jupiter only, that the recent advances in optical power 
and observing skill have only served to make more 
evident the thickness of the veil that obscures these 
objects in mystery. Analogy leads us a little way safely 
enough, but only to desert us before long. However, we 
must patiently watch and wonder. 
Other matters, too, might be noted before we take our 
leave of that brilliant disk, so easy of investigation, so 
difficult to interpret. Why are the shadows cast on it by 
the satellites sometimes so black, at others so dim, or so 
abnormally small? Why, when a satellite passes behind 
the limb, is it sometimes neatly bisected by it, at others 
visible behind or through it, either from optical projec- 
tion, as stars have been seen in front of the moon, or 
from the partial transparency of the edge of the globe? 
And then the satellites—they, too, have their anomalies 
in differences of apparent magnitude and brightness, due 
perhaps to variable obscurations of surface, but, if so, 
indicating conditions totally unlike that of our own | 
satellite—the presence of considerable atmospheres, the 
possible want of coincidence between their periods of 
revolution and rotation—or even a superficial constitu- 
tion as mutable and as hard of interpretation as that of 
the primary whom they obey. 
We shall not remove our telescope far before a still 
more interesting and surprising object will present itself 
in Saturn, now especially suited for investigation, both as 
to altitude and the presentation of the ring. If there was 
much in Jupiter to perplex us, there is far more here ; 
and it is rather mortifying to remark how little advance 
in knowledge has been made by the great increase, in 
recent years, of telescopic power. But little is ascertained 
now, beyond what was detected by the perfect vision of 
Dawes with his 63-inch Merz object-glass, or the beautiful 
definition of the 15-inch achromatic, by the same maker, 
at Harvard College. A study, in fact, of the memoir by 
Bond and his associates, in the Anza/s of that college, 
vol. ii. part 1, published in 1857, would be the best pre- 
paration for an intelligent scrutiny of this planet. But 
not much beyond a general impression can be expected 
from ordinary telescopes. It will require considerable 
power, as well as light and sharpness, to detect Encke’s 
subdivision of the outer ring (which, however, I caught 
in 1880 with my 93-inch mirror), to trace any possible 
subdivisions of the inner ring, to ascertain whether, as 
Trouvelot thinks, the gauze veil is becoming less trans- 
parent in its outer portion, or to investigate those strange 
and puzzling outlines of the shadow of the ball on the | 
rings, which, noted in part by others, have been recorded 
in detail in the Harvard memoir. A copy is here given 
of one, but not perhaps the most remarkable, of their 
diagrams. 
Fic. 2. 
Such a contour could be only accounted for, if at all, 
by an amount of unequal thickness in the ring, which 
ought to be, but is not in the smallest degree, visible in 
the edgeways presentation. The success of Prof. Hall 
in detecting a bright spot of considerable permanency 
upon the ball encourages attention in that direction— 
especially as there are several previous records of such 
phenomena. To hunt for the smaller satellites with any 
but superior instruments would of course be waste of 
time, but it may be remarked that Enceladus has been 
seen by Ward with exceptionally keen sight and a 4°3 
inch Wray object-glass, by Franks with § inch ditto, by 
Pratt with an 815 inch ‘“‘ With”’ mirror, and by myself 
with 9°33 inch. Mimas, the innermost, has been detected 
with a 7-inch achromatic by Wray. Meyer at Geneva 
has found it of late nearly as bright as Enceladus, and 
thinks it may be variable. 
The morning skies at present are graced by Venus, 
not however a remarkable object in her gibbous phase ; 
and Mars, who is coming rapidly round by his opposition 
to the evening. The smallness of his diameter, about 
15”, is a great impediment, especially in the English 
sky, to the hope of success with his minor details, though 
it may be borne in mind that in the air of Milan, and with 
an admirably defining Merz object-glass of 73 inches, 
Schiaparelli has made many delicate observations ona 
scarcely larger diameter, and with exceptionally fine air 
has carried them down, strange as it may appear, to a 
diameter of only 6”. j } 
The only other of the larger planets now visible is 
Neptune, easily picked up by means of an ephemeris, 
and distinguishable from a fixed star, even in a small 
telescope, by its dull and steady light. It demands, 
however, a large aperture for the bringing out and sharp 
definition of its pallid disk; in the latter respect the 
great achromatics at Rome (9°3 inch) and Bothkamp 
(115 inch) were unsuccessful, but I have seen it neatly 
terminated with Huggins’s 15-inch object-glass. Its 
satellite, though glimpsed by Ward with a 4°3-inch achro- 
matic, is far too difficult for ordinary vision or common 
apertures; I have seen it however plainly with the 15- 
inch just mentioned. ; : 
Vesta, though possibly visible with the naked eye, is a 
mere brilliant point of less than 1” in the telescope. 
Some notes on the autumnal constellations will be 
cht forward in a subsequent paper, 
Sibeaes” a me T. W. WEBB 
(To be continued.) 
