342 
completely resolved. In Table I are listed the wave 
lengths of the night-sky emissions and their identifica- 
tions which are probably agreed to at present; ‘“‘h” 
. Wave Lrenetus In Nigut-Sky SpectrRuM 
In- In- In- 
nN ten-| Source A | ten-| Source A | ten-| Source 
sity sity sity 
10440 A No 4837) 4 | No,vk| |3982} 1 | Ne,vk 
8829 3 4824! 2 | Oo,h 3960] 2 
8770 4 4810 3949} 3 | No,vk 
8694 1 4798 3914) 4 
8659 6 4772) 2 | No,vk 
8628 6 4739) 0 | No,vk 3901) 2 
8515 1 4715] 1 | Novk| [3888] 2 | Neo,vk 
8496 3 3873} 2 
8466 5 4693 3854] 1 | No,vk 
8431 8 4682} 1 | Oz,h 3848 O2,b 
4670| 3 | O.h | [3833| 3 | Osh 
8398 6 4650) 1 | Ne,vk 3818) 2 
8379 2 4632) 1 3778] 2 
8346 | 12 4615] 1 | No,vk| 3752] 2 | No,vk 
8311 4 4604 No,vk 3740) 4 | Ozh 
8287 3 4581 
8102 1 4569 3704] 2 
8066 2 4552 O2,h 3673] 1 
8026 4 3661| 2 | No,vk 
7992 7 4535) 5 | No,vk 3637] 3 | Oo,h 
7965 6 4520) 2 3623] 1 
4488 No,vk 3597] 1 | No,vk 
7916 10 4478) 3 | Novk 3584] 1 | No,vk 
7885 5 4469 3071 
7356 7 4461 3554| 5 | Oo,h 
7821 6 4442] 2 | Ov, 3545| 4 | Osh 
7789 4 4421! 5 | No,vk 
7752 6 4408} 4 | Os, 3012) 1 
7717 8 4396 3497| 1 | No,vk 
7405 1 3483) 3 | O2,h 
7336 3 4378 No,vk 3469} 2 
7283 2 4360) 2 | No,vk 3460] 1 | O2,h 
4348 3452) 2 | O2,h 
7249 1 4327| 2 3433) 1 
7148 1 4316 No,vk 3424) 1 | No,vk 
7093 1 4286] 1 | Oo,h 3393] 1 
6364 2/0 4278 O»,h 3385| 1 | Oo,h 
6300 4|0 4270] 4 | No,vk 
5896 Na 4257| 2 3373} 4 | Oo,h 
5890 Na 4239) 1 3319} 2 | Ooh 
5775 3296] 3 | Os,h 
5675 4219] 0 | No,vk| [3284] 1 | Oh 
5577 O 4203 3264| 2 
4188 3230] 1 | Ooh 
5460 4180 3220] 2 
5320 4169) 4 | No,vk 3212) 3 | Oo,h 
5250 4158 Oz,h 3201) 1 | No,vk 
5160 4140) 2 | No,vk| {3191} 1 
5130 O2,h 4131} 1 
5090 2 | No,vk 4117] 1 3164] 1 | O2,h 
5040 2 4111 3157] 1 
5002 1 | Oo,h 3144|| 3 || Os, 
4960 1 | Novi 4088) 3 3133] 1 | Oo,h 
4931 3 4071) 5 | No,vk 3103) 1 
4063 Os,h 3095] 1 
4904 No,vk 4048] 3 | No,vk 3084] 1 | Oo,h 
4889 4018} 3 3029] 2 | Ov,h 
4869 1 | No,vk 4004 
indicates the Herzberg system of molecular oxygen, and 
“vk” the Vegard-Kaplan system of molecular nitrogen. 
Wave lengths 8829 to 6300 A in Table I were from the 
list of Meinel [19], and wave lengths 5896 to 3029 A 
from the lists of Déjardin [9]. The sources of the emis- 
sions whose identification seemed certain are given in 
Table I. The only atomic lines are the green line 5577 
and the red pair 6364, 6300, which are forbidden transi- 
tions of oxygen, and the yellow pair 5896, 5890 of 
sodium. All the remaining lines and bands are of molecu- 
THE UPPER ATMOSPHERE 
‘lar origin. The line at 10440 A of the first positive 
system of N2 is by far the strongest emission thus far 
observed, being about thirty times as intense as the 
green line 5577, the next most intense emission. It was 
discovered in 1940 by Stebbins, Whitford, and Swings 
[25], by means of a photoelectric cell and filters, and its 
wave length was determined within +25 A. It was also 
discovered independently by Herman, Herman, and 
Gauzit [15]. A group of lines 6580, 6530, and 6470 A, 
also due to the first positive system of No, were men- 
tioned by Déjardin, but were not listed by Meinel; they 
cannot be seen in Fig. 1C’, and have not been included 
in Table I.1 About 35 bands, which include the strongest 
blue-violet bands, were identified with the Vegard- 
Kaplan system of Ne, and about 33 bands, which include 
the strongest ultraviolet bands, were identified with the 
Herzberg system of Op. 
In addition, in Table I, there are a number of un- 
identified lines or bands due to unknown systems. A 
weak continuous background with a trace of Fraunhofer 
absorptions, which was mentioned in earlier work, was 
not observed in the better, more recent spectrograms. 
It was this background which was attributed to sun- 
light scattered by material in interplanetary space. But 
since its existence is now uncertain one may be doubtful 
of inferences based on it. The Shumann-Runge system 
of O, and the Lyman-Birge system of Nj have been 
looked for, but no certain identifications have been 
made; the same is true for CO and CO», Hs, O03, NOs2, 
N2O,, N.O, N203, Nb, NH, CH, CN, HO, and 
compounds of Na, Sz, and S. 
The spectral intensity distribution received at the 
surface of the earth [6] is given approximately in 
Table II. 
Tasxe II. Intensity or Nigut-Sxy Emissions 
Mave icasth Emitter Ce 
10440 N2 190 X 1074 
6300, 6363 O 5 X 10-4 
5890, 5896 Na 0.7 X 104 
5577 O TSK Gr 
Main band systems N2, O2 10 X 1074 
The only reported spectral energy distribution of the 
night-sky light is that of Babcock and Johnson [3] 
derived from measurements of a small photographic 
spectrum of dispersion 1100 A mm at Hy. Their curve 
is given in Fig. 2; it rises with increasing wave length 
throughout the extent of the spectrum from 3800 to 
6500 A, with bumps at the various lines and bands A 
color temperature of 3450KK was ascribed to it. Thus 
the night-sky light may be said to be yellowish in 
color. 
Variations 
If we exclude polar aurorae, the variations in the 
total intensity of night-sky emission are relatively 
1. In a private communication Dr. Meinel stated that 
photometric traces of his spectra showed a faint feature 
centered at 6562 A. 
