556 
ME. W. HUGGINS ON THE SPECTEA 
the brighter central part of the coma. The circular form of the coma was uninter- 
rupted on the side of the tail, which appeared as an extension of the faint nebulosity 
which formed the extreme margin of the coma. 
The bright roundish spot of light in the centre, when examined with eyepieces mag- 
nifying from 200 to 600 diameters, presented merely a nebulous light without a defined 
form. 
Spectrum of the Comet . — When a spectroscope furnished with two prisms of 60° was 
applied to the telescope, the light of the comet was resolved into three very broad bright 
bands, which are represented in the diagram. 
In the two more refrangible of these bands the light was brightest at the less refran" 
gible end, and gradually diminished towards the other limit of the bands. This grada- 
tion of light was not uniform in the middle and brightest band, which continued of 
nearly equal brilliancy for about one-third of its breadth from the less refrangible end. 
This band appeared to be commenced at its brightest side by a bright line. 
The least refrangible of the three bands did not exhibit a similar marked gradation 
of brightness. This band, though of nearly uniform brilliancy throughout, was perhaps 
brightest about the middle of its breadth. 
These characters, which are peculiar to the light emitted by the cometary matter, 
must be distinguished from some appearances which the bands assumed in consequence 
of the mode of distribution of the light in the coma of the comet. The two more refran- 
gible bands became narrower towards their most refrangible side, as well as dimi- 
nished in brightness. This appearance was obviously not due to any dissimilarity of the 
light in the parts of the coma, but to the circumstance that as the light of the coma 
became brighter towards the centre, it was emitted by a smaller area of the cometary 
matter. The strong light of the central spot could be traced the whole breadth of the 
band ; but the light surrounding this spot, in proportion as it became fainter and broader, 
was seen for a shorter distance, so that the light from the faintest parts near the margin 
of the coma was visible only at the brightest side of the band. Since in the least 
refrangible band a similar gradation of light did not take place, this band appeared of 
nearly the same width throughout. 
The increasing brightness of the coma up to the brilliant spot in the centre showed 
itself in this band as a bright axial line fading off gradually in both directions. 
On this evening I took repeated measures of the positions of these bands with the mi- 
crometer attached to the spectroscope. These measures give the following numbers for 
the commencement and termination of the three bands on the scale adopted in the 
diagram. 
I could not resolve the bands into lines. When the slit was made narrow the bands 
became smaller both in breadth and length, from the invisibility of the fainter portions. 
I suspected, however, the presence of two or three bright lines in the bright central part 
