152 PROFESSOR A. S. HERSCHEL ON 
not be only apparent, but may have a natural signification. This easy measurement with high 
dispersion will serve as a small pendant to the vast stock of observations with lower power set 
forth by Professor P1AzzI SMYTH in the foregoing paper, in illustration of the prodigious mul- 
titudes of details observable in a single shaded band, with the spectroscope’s utmost resolving 
power. 
In comparison with other observations it may also, perhaps, suggest hypotheses of some 
slight use and interest for future explanations, in the confident hope which may now be fairly 
entertained, that the speeding advances of theory and observation will at no very distant time, 
by their joint discoveries, penetrate the physical meaning, and interpret the beautiful chromatic 
harmony of these close-ruled spectral bands. 
Micrometer Readings Wave-numbers to an Micrometer Readings Miong-Rno pers toan 
(revolutions). inch, , “a See 2 (cont na Te d.) roe, 
SSS SS verage a Se i Taverne 
| F Intervals. . - itron} 7; ners 
Intrusive Blow- eae Lines and Tatereal ioe Berne “Band piace Intervals, (continued.) 
pipe Citron Lines. manelets! Linelets. (continued.) ae (continued.) (contd.) 
28°500 (citron (45,066) 29°994 45,733 
line, 1). 28 °893 45,260 25 _——. 45 
*950* 285 15 30°098 45,778 47 
‘978 300 12 30°245 (citron "205 825 8 inter- 
29008 312 13 10 intervals line, 3). (45,840) | 50 vals 0f50°37 
035 325 15 of 13:0 B25 875 49 each = 4 x 
068 340 16 || each (2) - 448 924 53 12°59. 
*100* 356 17 “iD 977 49 
"138 373 17 ‘700 46,026 5a 
177 390 "850 084 a) 
——-——| 20 )} ( 980 136 
225 410 bathed 31°000 (citron — 
= 21 6 inter- Fi 
277 431 : line, 4). (46,146) 60 . x 
335 sy | 8 ieee es 31124 160 |e | ee 
29360 (citron (45,468) | 25 rae é -280 258: lp laches 
line, 2). "395 482 | 36 | ‘ 440 Bye | an loge 
470 area (eb {81-700 (citron, “605 386 J 
538 542 line, 5). (46,420) 66 
— 34°) | Cert 452 56? 
616 576 36 5 inter- ——_—— : 
“702 612 39 vals of 38°8 930 2 508? | ga9 
“796 651 40 each = 3x | 32°100? 5712 85? 
"894 691 49 12°98. \) BRP Ba! 656 ? : 
994 | 733 J | 
The linclets end here in haze. 
Citron-band in an end-on CO, tube, with intrusive blowpipe citron lines. Prism 9; dispersion 33° from A to H. 
April 1879. N.B.—The linelets of this group from wave-number 45,400 onwards (width 1 or 2 wave-numbers), are 
really exceedingly close pairs, opening gradually in width to 30 wave-numbers apart at last, but each pair is only noted 
here by its mean place, as if it were a single linelet. 
A similar set of measurements to these was taken very rapidly in July 1879, of the fluted 
spectrum of Nitrogen, a translation into wave-numbers of the excellent Table of that spectrum 
in ANastrom and THALin’s Memoir on “The Spectra of the Metalloids,’+ having presented un- 
mistakable indications of an arithmetical progression in the wave frequencies of its lines in the 
red to green portion of the spectrum. Tubes of sufficient purity to show this Nitrogen close- 
fluting or serration without interruptions or obliterations from the red to the green end, are 
however of rare occurrence; and neither those of air, nor of Nitrogen and its oxides presenting 
* Dull and band-like ; probably double lines (?) 
+ Nova Acta Reg. Soc. Se. Upsal., Ser. iii. vol. ix. 
