C. A. Young— Observations on Encke’s Comet. 83 
The spectrum of this comet appears to be the same with that 
of comet IT, 1868 (Winnecke’s comet), described by Mr. Hug- 
gins in the Philosophical Transactions for that year. No data 
are given in the paper by which to refer the scale of his instru- 
ment to that of Kirchoff, except such as can be deduced from 
inspection of the figure. The scale appears, however, to be the 
same as that used in his observations of star spectra (see Philo- 
sophical Transactions for 1864, p. 485). If so, D corresponds 
to 1000, E to 1252, & to 12975, and F to 1483. Assumin 
these numbers, I find that the relation of this scale to that of 
my own instrument is very closely represented by a straight 
line, and that the readings 1094, 1298 and 1589, corresponding 
to the lower edges of the bands observed, give respectively wave- 
lengths of about 559, 517 and 469 millionths of a millimeter. 
r. Huggins considers that he has satisfactorily identified 
this spectrum with that of carbon. 
_ The brightest line falls in the 6 group, where also a strong 
line appears in the spectrum of common air under the influence 
of the electric spark ; although quite probably merely accidental, 
it may also be worth noting that the principal line of the aurora 
spectrum (wave-length 5568) very closely coincides with the 
lowest band. 
On the evening of Dec. Ist, at 6" 04™ Pp. m., Hanover mean 
time (5% 45™ Washington time), the comet passed centrally over 
a star of the 9th magnitude. 
My attention was called to it by the sudden appearance of a 
bright, narrow spectrum running longitudinally through that 
instrument appear to have been several.times disturbed and adjusted during the 
series of observations embodied in his map. I subjoin a table, which I have often 
—. convenient, coordinating the two scales, derived from direct comparison of 
€ maps. 
Comparison of the Scales of Angstrom and Kirchof. 
Ang. K. Diff. ! Ang. K. pitt, || Ang. x. | Dim 
ee! _—<$<———$ — 
69 
4300 | 2867 5100 | 1747 ot 5900 | 1000 | Fey 
4400 | 2693 | 174 || 5200 | 1611 | j59 || 6000 
4500 | 2537 | 156 | 5300 | 1489 27 || 6100 895 | 5p 
4600 | 29397 | 14° || 5400 | 1392 97 || 6200 84 
4700 | 2268 | 129 | 5500 | 1304 8 || 6300 noo | 49 
4800 | 2147 | 12111 5600 | 1219 | yy o | 767 
4900 | 2030 | 117 || 5700 | 1142 v3 || 6500 1 |. be 
1s92 | 138! sg00 | 1069 ‘|| e600 680? 
oa td C (694 K) no accurate coérdination of the scales seems possible, as only 
Ty lew lines are recognizable on Angstrém’s map. é 
There is very great need Bg new map of the solar spectrum equally minute 
and faithful in detail with that of Kirchoff, but constructed hout on a con- 
Sistent scale; and for this purpose I am convinced that a scale of a 
, a8 already proposed by Herschel and Stoney, would be incomparably 
Most convenient for practical use 
