417 
SCIENTIFIC SUMMARY. 
ASTKONOMY. 
^PECTRUM Analysis of Co7net II. 1868. — On July 2, Mr. Huggins 
communicated to tlie Hoyal Society an important paper on the comet 
discovered by Winnecke a fortnight before that date. He found that on 
June 22 the comet presented in the telescope the appearance of a circular 
coma, at the centre of which there was a nearly circular spot of light. A 
faint tail could also be traced to a distance of about one degree from the 
nucleus. In the spectroscope the comet’s light was resolved into three broad 
bright bands. The brightest extended from near h about three-fourths of 
the way towards rj another lay beyond P: and the third band was 
between d and E. In the two former bands the light was brightest towards 
the less refrangible end of the spectrum, and diminished towards the other 
end. The third band was brightest in the middle. The bands could not 
be resolved into lines. The spectrum of the comet was found to agree 
exactly with a form of the spectrum of carbon obtained by takiug induc- 
tion sparks through olefiant gas. This form of the carbon spectrum 
had been observed by Mr. Huggins in 1864. On June 23 he instituted a 
direct comparison between the spectrum of the comet and that of carbon. 
The bands were foimd not only to agree in position, but in relative 
brightness and general appearance. The lines due to the hydrogen of the 
olefiant gas were not seen in the spectrum of the comet. On June 25, Mr. 
Huggins repeated his observations with the same result. 
These observations are the first which have given exact information re- 
specting the substance of a comet. The other comets which have been sub- 
jected to spectroscopic analysis have presented spectra which indicate the 
general character of the comet’s substance, but not one of the spectra has 
corresponded exactly with the spectrum of any of the terrestrial elements. 
It seems difficult to understand how it is that carbon can be volatilised in 
the interplanetary spaces ; but we do not as yet know enough respecting the 
conditions under which substances circumstanced as cometary matter is 
emit light, to enable us properly to estimate this difficulty. Certainly some 
comets have approached near enough to the sun to be subjected to an in- 
tensity of heat sufiicient to account even for the volatilisation of such a sub - 
stance as carbon. 
The Great Total Solar Eclipse . — "We have now received intelligence from 
four of the observing parties. Dr, Janssen, who headed the French expe- 
