276 
the following values: 
(A) e X 10° e2 X 1075 es X 1075 
2100 12.82 10.50 4.07 
2144 6.17 9.30 4.01 
2150 6.70 8.81 3.70 
2200 5.49 7.21 3.25 
2250 4.10 5.73 2.86 
2300 2.63 4.31 2.57 
2350 2.69 3.10 1.87 
2400 1.47 2.10 1.37 
The formulas given above agree surprisingly well with 
observed data and are valid in the large pressure in- 
terval between P = 0.20 and 180 kg em, in which e 
varies by four orders of magnitude. 
Determination of the Ozone Amount. At first, we are 
interested in the total atmospheric ozone amount, which 
is customarily expressed in terms of the thickness x of 
a layer under standard conditions of temperature and 
pressure. The decadic extinction coefficient of the total, 
pure atmosphere above the observer, according to Ray- 
leigh, may be denoted by 8; the decadic extinction co- 
efficient of the total turbid atmosphere may be denoted 
by 6, and that of ozone by ex; correspondingly, let the 
total path of the sun’s rays, having a zenith distance z 
be m according to Bemporad (for the turbid layer, 
m = sec z because the turbid layer generally lies on 
the ground), and let » = sec ¢ for the ozone layer, with 
(3) 
sin 2 
1+ h/R 
where h is the height of the ozone layer and R the 
radius of the earth. For radiation of the extraterrestrial 
intensity Zo subject to ozone absorption in the Hartley 
band, we obtain 
sin ¢ = 
log J = log Ip — Bm — 6 see z — axy; (4) 
for a neighhoring wave length (\’ > X) subject to lesser 
absorption by ozone, we find 
log I’ = log Io — B’m — 6’ sec z — a’zp. (5) 
From equations (4) and (5), we obtain the amount of 
ozone as 
log Io/Ip — log I/I’ 
ts = / 
(@= an 
(6) 
@—p)m _ (6 — 5’) see a 
(= aye (a — o’)p 
The quantity (6 — 6’) may be neglected except in the 
case of dense haze [42, 79]. The constant log (Io/Io) 
is then obtained by plotting diurnal measurements of 
log (J/I’) — (8 — 6B’) mas ordinate versus u as abscissa 
and extrapolating to u = 0. 
The experimental apparatus must be of such con- 
struction that scattering within the spectrograph is 
avoided since this would be a serious disturbance, 
particularly in view of the pronounced intensity drop 
at the end of the spectrum. Dobson’s spectrophotom- 
eter [22] is particularly designed to avoid such errors. 
By means of a rotating sector, J and I’ are made to 
THE UPPER ATMOSPHERE 
fall, in rapid alternation, upon a photoelectric cell con- 
nected to an amplifying device. By a measured atten- 
uation with an optical wedge, J’ can be made equal to 
I, a condition mdicated by a zero amplifier output; 
in this manner, the ratio J/I’ is measured. As calibra- 
tion runs in Arosa and on the Jungfraujoch have in- 
dicated, the wave-length adjustment of the instrument 
depends not only on temperature but also on altitude, 
since the refractive index of quartz with respect to air 
changes with air pressure. Values obtained with the 
old photographic Dobson instrument [24] must be re- 
duced to 88 per cent of the indicated value [40]. For 
the purpose of increasing the sensitivity of the Dobson 
spectrophotometer, it has recently been the practice 
to replace the photoelectric cell by a photo-multiplier. 
Figure 1 shows the latest model of the instrument ac- 
cording to the catalog of its manufacturer, Beck of 
London [70]. 
Fie. 1.—The Dobson Spectrophotometer. 
The ozone near ground level is determined by essen- 
tially the same method, employing in place of the sun, 
moon, or stars [13] an artificial light source [44] rich 
in ultraviolet and located at a distance of several kilo- 
meters. Improved chemical ozone determinations have 
recently gaimed extensive use [12, 20, 29, 73, 87, 91]. 
Determination of the Vertical Distribution. Two 
methods are available for determining the vertical dis- 
tribution of ozone. 
1. The Umkehr Effect. In the case of solar radiation, 
ozone absorption as well as scattermg is responsible for 
the fact that with increasing zenith distance 2, the in- 
tensity J of a shorter wave length (for instance \ = 3110 
A) decreases more strongly than the intensity J’ of a 
longer wave length (for instance \’ = 3290 A); the 
composition of light //I’ which we may also designate 
as light quality, decreases continuously as the zenith 
distance of the sun increases. For zenith radiation 7, 
the ratio 7/2’ shows a similar behavior at first, as long 
as the zenith distance of the sun is relatively small; 
