4.62 REPORT—-1904. 
ultra-red spectrum of ozone offers us a means of solving that question. The solar 
spectrum below \=4'6 p is certainly of little intensity and intersected by strong 
absorption-bands produced by aqueous vapour and carbonic acid ; the solar radia~ 
tion is, however, perceptible in all that space, and especially about A=4'8 and 
9°5 we know of no stronger absorption-bands caused by these gases. I have then, 
with the same spectrobolograph that I have used in the investigation of the 
absorption-spectrum of ozone at different times, registered the solar spectrum, 
and I have found that the band \=4°8 as well as A=9:1—10°0 are present in the 
solar spectrum. During the month of March these absorption-bands in the solar 
spectrum were of about the same intensity as those I have found by using the 
absorption-tube, but in June they were much weaker, and the band \=4'8 
scarcely perceptible. 
By this I have proved that— 
1. Ozone produces a strong absorption in the ultra-red spectrum, where it is 
characterised by several bands of great intensity. 
2. These bands are also present in the solar spectrum, where their intensity, 
however, is subjected to very great variations. 
3, Ozone is then present in the atmosphere, and must exercise a strong but 
variable absorption on the radiation from the earth. 
It is well known that sun-spots and the electrical phenomena in the terrestrial 
atmosphere are connected with one another. But it is also probable that these 
electrical phenomena are a cause of the production of ozone in the atmosphere, 
and consequently the absorption of the earth-atmosphere and the climate must 
to a certain degree depend on the sun-spots and vary with these. 
It is evident that only continued investigations can teach us how much and in 
what manner the quantity of ozone varies in the atmosphere. For the moment I 
will here only insist on the importance of these investigations, for which the 
spectro-bolometer offers a very convenient method. 
10. An Instrument for the Measurement of the Radiation from the Earth. 
Ly Professor K. Anastrom. 
A question that has hitherto been but too little studied is the radiation from 
the earth. It is, however, of the greatest importance, not only as a climato- 
logical factor of great interest, but also for our knowledge of the influence of the 
atmosphere on the solar radiation. : 
Very interesting investigations in order to determine the radiation from th 
earth in absolute measures have been made by Pernter, Maurer, and Homén, and 
lately by Exner, who has employed for these examinations my pyrheliometer with 
electric compensation, but there is no doubt that the screen used in these 
researches in order to intercept the radiation from space introduces certain errors, 
and that a satisfactory instrument for determinating the radiation from the earth 
has not yet been constructed. 
It seems, however, that a simple modification of my pyrheliometer witk electric 
compensation would lead to a very good result, and the instrument which I have 
constructed according to that principle has, during the time in which I have 
had the opportunity to test it, proved itself to be a reliable and convenient one. 
The modification of the pyrheliometer for that purpose consists only in 
exchanging the black strips of manganin for two platinum strips, one black, the 
other bright. These strips are placed beside each other in a little frame, Two 
thermo-elements are fastened to the back of these strips, and with a galvanometer 
it is possible to prove that the temperature of the strips is the same. The appa- 
ratus employed by the pyrheliometer are also used here, viz., a galvanic element, 
a rheostat to regulate the electric current, and an accurate amperemeter in order 
to determine the strength of current for heating the strips. 
The frame is fastened at the upper end of a bright metallic cylinder, which 
before the beginhhing of the observations is closed by a cover. By exposing the 
