< Page:The story of the comets.djvu
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66
Chap.
The Story of the Comets.

The Rev. H. C. Key, speaking in the first instance of what

he saw on December 3. said[1]:—

"The train following the comet was quite broad in my telescope, and could not be termed a 'ray'. You will observe two rays on the preceding side; these I have drawn as you see, but I am not perfectly certain that the effect was not in my own eye and not a reality. I took every precaution to find out; and at the time (as well as now) felt pretty well convinced that it was no illusion. Four or five times I left the telescope, and upon returning there were the rays in exactly the same spot and direction. I feel pretty confident of their reality (they were extremely faint), but, as I say, am not quite certain, as I sometimes see dark lines in the field when first going to the telescope. The comet never seemed to me to lose its elliptical form from the first night I saw it, Oct. 20. I detected a nucleus for the first time on Nov. 7. The train I mentioned before was much fainter than the main body of the comet, and I was able to trace it to a distance of about 32' from the nucleus. I saw nothing like the drawing of the comet made at Greenwich."

The return of 1871 was also important because it was found not to have been accelerated in accordance with the Resisting Medium theory as previous returns had been, since the first discovery of the comet in 1786. Von Asten's conjecture as to this is that in 1869 the comet might have come into collision with some minor planet which violently deranged and modified its orbit in some degree.[2]

Passing over the returns of 1875 and 1878 we come to that of 1881, in which year the comet passed through perihelion on Nov. 18. Common, using a 3-ft. reflector, noted the comet to be about 2' in diameter, very faint even in an instrument of that size, and with slight indications of an increased brightness in the centre. Tacchini found the spectrum exhibiting bright bands in the yellow, green, and blue respectively, coinciding with the 3 principal bands seen in the spectra of the hydro-carbons. As in the case of some other comets, the bands were shaded off to the blue. A faint continuous spectrum was also detected.[3] The spectrum was considered to have undergone no change since the previous examination in 1878.

Since 1881 Encke's Comet has returned and been observed

  1. ↑ Month. Not., vol. xxxii, p. 217. March 1872.
  2. ↑ Bulletin de l'Acad. de St. Pétersbourg, vol. v; Observatory, vol. i, p. 21, April 1877.
  3. ↑ Comptes Rendus, vol. xciii, p. 947.
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