W. Harkness— Observations on Comet 6, 1881. 187 
three fine, bright lines upon it, one just at the lower edge of 
the band, and the other two at distances of about 30 Angstrom 
units—coinciding apparently with three lines which are seen in 
the Bunsen flame spectrum, though I did not succeed in meas- 
uring them 
It is hiaedly necessary to say that the evidence as to the 
identity of the flame and comet spectra is almost overwhelming ; 
the peculiar i defined appearance of the cometary bands at the 
time of the comet’s greatest brightness is, however, something 
which I sales not yet succeeded in poiteine with the flame 
spectrum. The comet spectrum on July 25th certainly pre- 
sented a general appearance quite different from that of the 
later observations, as regards the definition of the bands. 
Perhaps I may be allowed to record here a fact which has 
nothing to do with the comet, but was observed while adjust- 
ing the a a ie upon the sun in preparation for evening 
; that the one-prism spectroscope shows the bright 
lines in she upper portion of the chromosphere spectrum, above 
h, better than any other instrument I have yet tried. I have 
hitherto always found it rather difficult to exhibit the two H’s 
as bright lines to a person unused to the spectroscope, but with 
this instrument they are perfectly obvious—even = trusive. 
The only (and indispensable) precaution needed is to put the 
slit accurately in the focal plane of the telescope for these 
special rays, 
Princeton, July 14. 
T. XX VI.—WNote on the Observations 7 Comet b, 1881, segs 
vel ‘the United States Na val Observatory; by WM. HARKNE 
{Communicated by eres, 8 of Rear Admiral John Rodgers, U. S. N., 
Superintendent. | 
On the evening of June 28th, I examined the comet for 
polarization by means of a double image prism applied to the 
naked eye, and at first I fancied that when the two images were 
placed in the axis of the tail the one situated farthest forward 
was the fainter, but a careful examination by three different 
observers rendered this doubtful. Recourse was then had to a 
three-inch telescope armed with an eye-piece magnifying 34°5 
diameters, and the image of the comet given by it was exam- 
ined, first with the double i image prism, and subsequentl Pe 
a Savart polariscope, but neither of these instruments s 
any polarization. Mr. Huggins thinks he has detected’ the 
