asna.18510320702

A S T K 0 N 0 M I S C H E N A C H K I C I3 T E 8.
NP. 751.
On
S O I ~ C new
Phenomeua in the Ring of Saturn, by the Rev. W . I?. Unwas.
February 10, 1851.
Watrriiighury near Maidstoile, Kent,
In
the autumn o f last year I removed m y observatory tn
this place froni niy foriiier residence , Camden Lodge, Cranbrook. T h e telescope i s air ecpatoreally niniinted refractor Iiy
the dark houndary betmeerr the bright and the faint ririgs did
not appear so absolutely black as the interval between t h e
t w o bright rings; and I h a d therefare imagined the faint zone
M e r z and So:i of Munich, having ail apertilre c t f 6 iriclirs,
arid a focal leiigth of 8 fect: Pari: measure.
O n Nnv. 25, 1850. the air wag very favoral)le i n the
w i t h power 4 2 5 , I was astonished a t the
appearance o f a fairit light extending over rather more tlian
one third o f the interval I)etweeii the iriuer edge of tlie bright
to be attached to the ring, though differing greatly i r i reflective power. 50 doubt Mr. Bond's view o f it i s correct. But
as no further details o f h i s discovery have been received in
this country, so far as 1 know, all my iut'ormation respecting
tliis new pheriomenorr is derived from m y o w n telescope, ex.
cvpt the actual s e p a r a t i n n o f thc faint ring from the bright
one.
r i n g and the ball. I t was w i t h great difficulty that I arrivcd
a t the conclusioir that this was n reality : aud before 1 had
On three oiglits 1 have obtainrd micrometrical iaeasuree
o f the distance of the inner edge o f the obscure ring from the
early part o f the evcning.
Having turned tbe telescope t o
the planet Saturii,
4'
satisfied myself on this point, niy observations were iritcrrupO r i returning to them, I found the air had heconie
tcd.
inner edge o f tlre bright ring. T h e nhservations, which were
extremely clillicr~lt, give the following results, rcduced t o t b e
mean distance o f Saturn. Magnifying power 375.
greatly disturbrd , and riothing further could he discovered.
T h e nest fine iiight occurred on Xov. 29. W i t h power
1850 1)c.c.
460, the same plierinniiwm was again observed. There appeared to be n continuatioil of the breadth of the ring towards
the ball, extremely failit, as if cilp;ible of reflecting very
littlr ligbt. A (lark and rattier auddeii sliadirig off w a s observed to foriii a bouiidary between this dull zone atid the
bright ring; the hreadth of the zone being about t w o thirds
the breadth o f the outer ring. 9 t the interior edge of the
ring where it crosses the ball, a v e r y n a r r o w d a r k l i n e
was noticed, which became broader towards the east and
west edges o f the planet. I concluded that this dark line
w a b the projection o f the obscure zoiic, the full breadth o f
1851 Jan.
'LO
22
l"807 b y G observations:
1,967 ,, 6
9,
23
1,958
M r a n , allowing
weights,
= ..
,, 10
3s
weight
=6
9,
10
,;
32
1,941 by 22 observations.
1 bave frequeiitly received the impression o f the obscure
r i n g beirrg divided ioto t w o , or else composed of t w o zones
o f different reflective power: the one which is nearest to the
which i s firen a t the arisae. These observations were entered
a t the time in niy observatory journal, and a diagram made
planet being fainter, a n d also narrower, than the other. On
several h e days the observations have heeu begun i n daylight, and the time noted when the different parts became
visible a s the light faded. First appeared the portion furthest
from the planet, and separated f r o m the bright ring by a
i n i t to illustrate m y description.
dark boundary ncarly equal iii breadth t o the p r i m a r y divi.
T h e accompanying picture
i s taken from t h a t diagram, corrected only as t o the forni
o f the ellipse.
011Dec. 2, m y frirnd Mr. Lassell, o f Starfield near Liverpool, visited m e ; and, the evening o f the 3 d provirrg firre,
we both distinctly saw the phenoiiiena recorded above.
00 the mnrning n f Dec. 4tb, I sd\v a paragraph i u T h e
T i m e s irewspaper, announcing that Mr. Band, a t Canibridge
irr the U n i t e d States,
h a d discovered an interior very faint
ring o f Saturu, by the help o f the large refractor b y Mmz,
having an aperture of 14 French inches. I n my telescope,
SPr
Bd
-
sion between the brigbt rings;
i t s outer aud inner edges
presenting an elliptic curve pretty well delilied for so fairit an
It extends t o about one third o f the divtauce betwceo
the brigbt ring and the ball. I n about 12 minutes afterwards
the inner edge of the interior portion became visible, an extremely narrow dark boundary or division lying between the t w o
object.
,
i
i
I
portions. I have also observed that when the obscure ring,
taken as a whule, i s best seen, i t i s not o f u n i f o r m
brightness, the outer portion being the brighter: arid in ordiiiary statea o f the air, this outer portion alone i s visible;
7
99
Nr.
while, during occasional intervals of better vision, and ou
very Grre nights, the inner portion also is ween.
Supposing t h a t , according to Struvc's measures, the
751.
100
interval hetween the interior bright ring and the ball is 4%.
I have estimated the breadth of the tliffercnt purtions nearly
as follows: -
....................0"3
.................................... . 1 . i
.....0 - 6
......2,o
.................?,sa
Interval between hright ring and exterior ohscare ring
Breadth of exterior ohscure ring
Breadth of interior obscure ring and (lark 1)ouridary between the t w o
Sun1
Interval between inner edge of obscure ring and the Iball
I have always o-eerved that the upper and more distant
part of the ohscure ring is more plainly seen than the corresponding part on the side nearest the earth: and also that
its projection a t the niinor axis of the ellipse, seen on the
planet as a dark line of elliptic form, i s considerably narrower
than accords with its hreadth at the major axis. To avoid
the effect of irradiation in diminishing its apparent breadth
I have carefully examined this dark line in daylight and strong
twilight, when the air was quirt arid the image sharply defined. B y comparison of its brcadth w i t h that of I spider's
web of the micrometer, 1 concluded it to be not more than
from 0'12 to 0 ' 1 ~ 5 a t the niinor axis; which, for the time of
observation, corresponds to a breadth o f from l"08 to t"35
a t the major axis. T h e appearances would he satisfied b y
supposing that a section of !he obscure ring may he somewhat w e d g e - s h a p e d , the thicker edge heing outwards;
and that a sectiorr of the bright ring nlay also be wedgeshaped, its thickest edge being inwards: - thus
-
C
7
-
T h e same supposition might also tend to account for the
outer edge of the shadow of the ball upon the ring appearing
slightly c o n v e x towards the hall; a s 1 have dwilys observed it during this apparition of the planet. B u t perhaps this
may he only the effect of c o n t r a s t with the much greater
curvature of the edge or the ball, influencing the judgment
of the eye. It may ;ilso he qucstioiietl whether the thickness
of the ring can be sufficient to allow of the requisite variation
of substance in its different parts. Would it not he seen
when its plane passes through the earth, either as a hriglit
line on each side of !he ball, or as a dark liue of consideralile breatlth on t h r ball itself?
The P l a n e t S a t u r n
as seen at Watcringbury near Rlaitlstone on Koreniber 29, 1850
by W . R. Dames.