Survey of Northeast Greenland. 191 
. . 4 L2 а 
abscissa line as for К, the values Да = a+ are formed, corre- 
sponding to the values 4k. 
The connection between the actinometric difference and the co- 
efficient of refraction is not very obvious in the table, but never- 
theless it appears extremely clearly in the diagram, in particular if, 
as in the curves given in Fig. 16 of values of Ja and 4k belonging 
together, the ordinates of the two curves are given opposite signs. 
In spite of the paucity of the material, particularly as far as the 
co-efficient of refraction is concerned, Fig. 16 gives a very distinct 
hint as regards the connection between the actinometric difference 
and the co-efficient of refraction HF in that the figure gives us an 
incomplete picture of two curves of sine the phases of which show 
a difference of a couple of hours. A picture of this kind must indeed, 
seem a very plausible one. 
An attempt to penetrate further into the problem here set forth 
would presumably, at the present moment, be quite futile, as the 
necessary material of observation is hardly to be found anywhere. 
A further development of the problem would therefore in far too 
high a degree be based upon closet reflections. 
Special observations. Examples of anomalies 
of refraction. 
When we commenced the observations at Danmarks Havn, with 
the object of determining the magnitude and variation of the co-effi- 
cient of refraction, we had not realized the close connection between 
the co-efficient of refraction and certain meteorological factors. How- 
ever, we were rather quickly taught by experience that such a close 
connection existed, which led to the result, that wherever circum- 
stances permitted, we levelled simultaneously with kite- or balloon- 
ascensions or with measurement of temperature in the crow’s nest, 
In this manner it appeared that one might generally, with a cursory 
glance at the automatic diagrams from the kite- or the balloon- 
ascensions, form conclusions as to the tendency of the results of 
levelling, just as one might reversely from the levellings form certain 
conclusions as regards the existence and position of inversions 
&с. &с. By comparing the material already published, anyone may 
convince himself of this. A single very pronounced example is pro- 
vided by the ascensions of kites and the levelling on October 21st 
1907. 
The journal of levelling for the observation series of 8230 shows 
the following result (instead of the readings I give 4z with the same 
value as in the tables on pp. 156—157 and p. 162). 
XLVI. 13 
