278 
later. From the ground upwards, the region of known 
ozone concentration could today easily be extended from 
5 to 10 km above ground by modern aerological methods 
(chemical measurements by airplane). A subdivision of 
the region between 10 and 35 km into three shells would 
then remain for the Umkehr measurement. Day-to-day 
measurement of these three layers would be of the most 
important meteorological interest. 
2. Techniques Using Recording Balloons, Stratospheric 
Balloons, and V-2 Rockets. In addition to the rather 
indirect method involving the Umkehr effect, there is 
of course the challenge of sending spectrographs to ever 
higher altitudes until finally the ozone layer is pene- 
trated. The first great success in this respect was 
achieved by E. and V. H. Regener on July 31, 1934 
when they sent a recording spectrograph to an altitude 
of 31 km by means of a balloon [85]. The lightweight 
spectrograph was pointed downward against a horizon- 
tal magnesium oxide disk exposed to sunlight; magne- 
sium oxide effectively reflects ultraviolet. The apparatus 
is installed in a light wooden frame, the lower half of 
which is covered with aluminum foil, the upper half 
with cellophane, an arrangement which affords ex- 
cellent protection against cold. The photographic plate 
Fig. 4) is rotated through a small angle every ten 
Fig. 4.—Regener-photographs of the ultraviolet spectrum 
taken in the stratosphere. 
minutes, being continuously exposed in the meantime. 
At the instant the plate is advanced, a small hight bulb 
is turned on by which the readings of two aneroid 
gauges (standard barograph and low-pressure baro- 
graph) as well as of a bimetallic strip to dicate the 
temperature of the instrument are recorded. On the 
plate which has a diameter of 10 cm the step-shaped 
interruptions of the long rays are the shadows of the 
two indicators connected to the aneroids; they represent 
lower pressures the closer they approach the center. 
The clear ultraviolet spectra are located diametrically 
opposite the pressure indications and they are seen to 
extend to shorter wave lengths the greater the altitude 
THE UPPER ATMOSPHERE 
and the smaller the quantity of ozone traversed by the 
solar radiation. In addition, the plate also bears a mer- 
eury calibration spectrum. The entire device, including 
a protective frame, weighs 2.7 kg. If \, represents the 
shortest wave length of the solar spectrum at an alti- 
tude h, and zenith distance z,, and if x, represents 
the total quantity of ozone located above the instru- 
ment, then, approximately, 
Zoalo SEC Zo = XQ, SEC 2. (9) 
Further improvements are obtained with an accurate 
intensity measurement at the end of the spectrum and 
elimination of diffuse sky light, for instance with the 
aid of a magnetically oriented hemispherical stop [86]. 
Coblentz and Stair [15] and Stranz [91] attempted to 
simplify the methods by replacing the spectrograph by 
a cadmium cell and filter as was done in the first ozone 
measurements in 1921 at Arosa. The intensity values are 
transmitted radiotelegraphically as in the radiosondes. 
With the aid of a free balloon, A. Wigand as early as 
1913 measured the ultraviolet end of the solar spectrum 
up to a height of 9 km. Shortly after the Regener ex- 
periments, the stratosphere balloon, which is capable of 
carrying aloft high quality imstruments, was employed 
for this purpose. Under the leadership of Stevens and 
Anderson, Explorer II reached an altitude of 22 km 
in November 1935; ozone at even higher altitudes was 
determined indirectly from the sky radiation [89, 69]. 
Ozone determination by means of captured V-2 rockets 
[95] represents the climax of this brilliant development. 
It was the fulfillment of a dream when on October 10, 
1946 in White Sands the ozone layer was penetrated 
and a large unknown range of the solar spectrum be- 
came accessible (Fig. 5). 
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DSI 
Peek 
ALTITUDE (KM) 
Nu a 
Sis 
ee 
$5 
2 
2 ANGSTROM UNITS SENS 
. 5.—Short-wave end of the solar spectrum taken from 
V-2 rocket. 
RESULTS OF OBSERVATIONS 
The Ozone Amount. The first ozone determinations 
made in Marseille [82], as well as the measurements 
made at Arosa with filtered cadmium cells since 1921, 
revealed irregular ozone fluctuations from day to day. 
Dobson [24] discovered their connection with the gen- 
eral distribution of air pressure so that they may be 
designated as meteorological fluctuations. The interdiur- 
nal variability of the ozone amount at Arosa was found 
to be: 
cm cm cm 
January 0.017 May 0.011 September 0.008 
February 0.017 June 0.010 October 0.009 
March 0.015 July 0.010 November 0.010 
April 0.015 August 0.009 December 0.013 
