88 
NATURE 
[ Fmone: Tere 


THE SPECTRUM OF URANUS * 
ie the paper “On the Spectra of some of the Fixed 
Stars,” + presented conjointly by Dr. Miller and | 
myself to the Royal Society in 1854, we gave the results 
of our observations of the spectra of the planets Venus, 
Mars, Jupiter, and Saturn ; but we found the light from 
Uranus and Neptune too faint to be satisfactorily examined | 
with the spectroscope. 
By means of the equatorial refractor of 15 inches aper- 
ture, by Messrs. Grubb and Son, recently placed in my 
hands by the Royal Society, I have succeeded in making 
the observations described in this paper of the remark- 
able spectrum afforded by the light of the planet Uranus. 
It should be stated that the spectrum of Uranus was 
observed by Father Secchi in 1869.¢ He says, “ Le jaune 
y fait complétement défaut. Dans le vert et dans le bleu 
il y a deux raies trés Jarges et trés noires.” He represents 
the band in the blue as less refrangible than F, and the 
one in the green as near E. 
The spectrum of Uranus, as it appears in my instru- 
narrow spectrum placed above that of Uranus gives the 
| relative positions of the principal solar lines, and of the 
two strongest absorption-bands produced by our atmo- 
sphere, namely, the group of lines a little more refrangible 
than D, and the group which occurs about midway from 
Cto D. The scale placed above gives wave-lengths in 
millionths of a millimetre. 
The spectrum of Uranus is continuous, without any 
part being wanting, as far as the feebleness of its light 
permits it to be traced, which is from C to about G. 
On account of the small amount of light received from 
this planet, I was not able to use a slit sufficiently narrow 
to bring out the Fraunhofer lines. The positions of the 
bands produced by planetary absorption, which are broad 
and strong in comparison with the solar lines, were deter- 
mined by the micrometer and by direct comparison with 
the spectra of terrestrial substances. 
The spectroscope was furnished with one prism of 
dense flint-glass, having a refracting angle of 60°, an ob- 
serving telescope magnifying 53 diameters, and a colli- 
mator of 5 inches focal length. A cylindrical lens was 
ment, is represented in the accompanying diagram. The used to increase the breadth of the spectrum, 
¥ i a 
47 48 99 SO SI 52 53 Sh SS 56 S57 A 59 60 Ci G2 GS Ch GS GE 
tit u 


The remarkable absorption taking place at Uranus 
shows itself in six strong lines, which are drawn in the 
diagram. The least refrangible of these lines occurs in | 
a faint part of the spectrum, and could not be measured. 
Its position was estimated only, and on this account it is 
represented in the diagram by a dotted line. The posi- 
tions of the other lines were obtained by micrometrical 
measures on different nights. The strongest of the lines 
is that which has a wave length of about 544 millionths 
of a millimetre. The band at 572 of the scale is nearly 
as broad but not so dark ; the one a little less refrangible 
than D is narrower than the others. 
The measures taken of the most refrangible band 
showed that it was at, or very near, the position of F in 
the solar spectrum. The light from a tube containing 
rarefied hydrogen, rendered luminous by the induction- | 
spark, was then compared directly with that of Uranus. 
The band in the planet’s spectrum appeared to be co- 
incident with the bright line of hydrogen. 
Three of the bands were shown by the micrometer not 
to differ greatly in position from some of the bright 
lines of the spectrum of air. A direct comparison was 
made when the principal bright lines were found to have 
the positions, relatively to the lines of planetary absorp- 
tion, which are shown in the diagram. The band which 
has a wave-length of about 572 millionths of a millimetre 
is less refrangible than the double line of nitrogen which 
occurs near it. The two planetary bands at 595 and 618 
of the scale appeared very nearly coincident with bright 
* From the Proceedings of the Royal Society. 
{ . . 
| lines of air. 

The faintness of the planet’s spectrum did 
not admit of certainty on this point ; I suspected that the 
planetary lines are in a small degree less refrangible. 
| There is no strong line in the spectrum of Uranus in the 
position of the strongest of the lines of air, namely, the 
double line of nitrogen. 
As carbonicacid gas might be considered, without much 
improbability, to be a constituent of the atmosphere of 
Uranus, I took measures with the same spectroscope of 
the principal group of bright lines which present them- 
selves when the induction-spark is passed through this 
gas. The result was to show that the bands of Uranus 
cannot be ascribed to the absorption of this gas. 
There is no absorption-band at the position of the line 
of sodium. It will be seen by a reference to the diagram 
that there are no lines in the spectrum of Uranus at the 
positions of the principal groups produced by the absorp- 
| tion of the earth’s atmosphere. 
+ Phil. Trans. 1864, p. 413; and for Mars, Monthly Notices R. Ast. Soc. | 
vol. xxvil., p. 178. nes 
t Comptes Rendus, vol. Ixviii. p. 761, and ‘‘ Le Soleil,” Paris, 1870, p. 354. 
WILLIAM HuGGINS 


NOTES 
WE understand that the contributors to the next volume of 
the Zoological Record are as follows :—Mammalia, Reptilia, and 
Pisces, Dr. Albert Giinther, F.R.S. ; Aves, Mr. H. E. Dresser, 
F.Z.S., and Mr. R. B. Sharpe, F.L.S. ; Mollusca, Molluscoidea, 
and Crustacea, Dr. Edward von Martens, F.M.Z.S.; Arachnida 
and Myriapoda, Mr. O. Pickard-Cambridge, C.M.Z.S.; Insecta 
generally and Coleoptera, Mr. E. C. Rye; Lepidoptera, Mr. 
W. F. Kuby; Diptera, G. A. Verrall; Neuroptera and Or- 
thoptera, Mr, M‘Lachlan ; Rhynchota, Mr. John Scott ; Vermes, 
Mr, E, Ray Lankester ; Echinodermata, Ccelenterata, and Pro- 

