Survey of Northeast Greenland. 189 
fraction is in the main the same at Danmarks Havn as in other 
parts, seems to indicate that we are here dealing with quite a common 
factor of the co-efficient of refraction, the cause of which may thus 
be equally common. As such appear irradiation and radiation, which 
must be supposed to cause daily periodic oscillations Di 2 The 
actinometric difference may be considered as a measure of Patron 
and radiation; it is therefore natural to seek a connection between 
the latter and = or the co-efficient of refraction. 
The mean values of the actinometric difference 
and the co-efficient of refraction 
within the period НЕ 
Actinometric difference | Co-efficient of refraction 
SN ET | Hour | k= kn+ dk 
8a +141°C. | +3.8°C. | 
9a 159 00%! SS hl SaQi REE 01026 
la RAS +72 | | 
ES Tee pl chaman US km + 0.005 
1? RAS ANIME Cr 
Sp | 8 | 
i if a i a | 1p5 | km--0.016 
a + 143 +40 | 320 km - 0.078 
4p 1719.8 +25 | | 
5P | + 11.4 ain an | 
6p 109 | 
(i) are ne | 
SP — 6.8 | 95 | 7P.1 km —- 0.040 
IP | + 63 +40 | 
lo 4 SBAS sn or 9 903 km + 0.025 
MS | oe By CAG «| 
0 + 20 а | 
la + 19 2840 à | 
2a + 21 +32 | 
3a + 34 +69 | 
a2 ST ET | | 
5a Ce sd RE km + 0.072 
6a | + 10.2 о 
en 0 + 1.7 
Mean... | + 10.3 
On the Danmark-Ekspedition the actinometric difference was 
determined once in the course of every month by measuring every 
second hour through the twenty-four; the result of the measurings 
are given and treated in the frequently mentioned dissertation by 
BRAND: “Die Temperatur in der Ausguckstonne”. From the six series 
