46 Mr. W. Huggins on the Spectrum of Encke's Comet. [Nov. 23, 



its less refrangible limit, and gradually faded towards the blue. The 

 micrometer gave 5160 millionths of a millimetre as the wave-length of the 

 less refrangible boundary of the band. Two other bright bands were 

 occasionally suspected ; one of them appeared to be about two thirds of 

 the distance from the bright band towards D, the other a little distance 

 beyond F. No continuous spectrum could be detected. The nucleus was 



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probably much too minute and faint to give a continuous spectrum that 

 could be seen. 



No difference in the spectrum was seen when the slit was moved over the 

 comet in different directions, as far as its feeble light permitted. 



The spectrum of a hydrocarbon, giving the bands which appear to be 

 due to carbon, was then reflected into the instrument, and observed simul- 

 taneously with that of the comet. The band in the green was found to be 

 identical in position with the brightest of the bands of carbon, and to be 

 similar in gradation of brightness from its less refrangible limit. 



Nov. 9* The observations of yesterday were confirmed. The second 

 more refrangible band, which was then caught only by glimpses, was found 

 .to be coincident with the third band in the carbon spectrum. The wave- 

 length of the less refrangible limit was about 4735 mm . The least re- 

 frangible of the three cometary bands could be seen only occasionally. 



Nov. 12. The observations on this evening contain no new facts. 



Nov. 13. To-night the nucleus appears as a minute, well-defined stellar 

 point. 



In the spectroscope the three bands are distinctly seen. The position 

 in the spectrum of the least refrangible band corresponds with the first 

 band of the carbon spectrum ; it commences from the red, with a wave- 

 length of about 5632 mm . 



Attempts were made with a double-image prism, a Nicol's prism, and a 

 Nicol's prism combined with a Savart's system of plates to detect 

 polarized light in the comet, but without success. 



Nov. 14. The form of the comet remains nearly the same. The out- 

 lying nebulosity is now chiefly on the south of the axis of the comet. The 

 nucleus appears to be precisely at the extreme eastern limit of the brighter, 

 more condensed part of the comet. 



The same spectrum was seen, but fog coming on interrupted the obser- 

 vations. 



On this evening an attempt was made again to detect polarized light. A 



