xxviii GENERAL SUMMARY OF SCIENTIFIC AND 



No. Observed. 



I. Enckc's comet January 2G, 187"), by llolden, at Washington. 



II. Winnecke's comet February 8, 1875, by Stephan, at Marseilles. 



The fine comet which was visible in 1874, and known as 

 Co^^ia's comet, gave occasion for several interesting ol>- 

 servations, some of which have been published during the 

 past year. Among these, we notice those having a bearing 

 upon its physical constitution, such as Mr. Ranyard's polar- 

 iscopic observations, showing the absence of a sensible 

 amount of polarized light, whence he concludes that the 

 substance of the tail is either incandescent, or else made up 

 of atoms which are small compared with the wave-lengths 

 of the light. Mr. Christie's spectroscopic observations show 

 that in the spectrum of the comet two bright bands were 

 found on every occasion, sensibly coincident with the two 

 brighter bands of carbon dioxide. The spectrum of the 

 nucleus was continuous, and appeared to contain numerous 

 bright bands, and occasionally dark lines. The other ob- 

 servations, in so far as they have been published on this 

 body, were referred to in our previous volume. 



Secchi's observations of the spectrum of Coggia's comet 

 show that it agrees best with the spectrum of the oxides 

 of carbon ; but the polariscope shows that the continuous 

 spectrum was only the reflected light of the sun ; and Yogel, 

 in a general review of the questions relating to cometary 

 spectra, concludes that there is some probability that the 

 gases present in comets are hydrocarbons. 



Encke's comet, one of the faintest comets familiar to 

 astronomers, has been observed in the northern hemisphere 

 at Washington with the twenty-six-inch refractor, and at 

 Marseilles with the large reflector of that observatory. Ac- 

 counts of equally successful observations have also reached 

 us from the Melbourne Observatory. 



Winnecke's comet has been observed at the Harvard Col- 

 lege Observatory. 



Highly interesting analyses of two meteorites have lately 

 been made by Mr. A. W. Wright, of New Haven, which, be- 

 sides being valuable as careful determinations of the chemical 

 constituents of the two specimens examined, directly attack 

 the question of the relation of meteorites to comets. Pro- 

 fessor Wright finds that, under suitable conditions of press- 



