178 I. P. Kocu. 
apparantly rides on the’ top of the mountain, in which manner the 
wave becomes visible.) 
In the wave movement it is to be supposed that the chief reason 
of the above-mentioned vertical movement of the objects is to be 
sought, and so we also get an explanation why К oscillates more 
than x which is, in many cases, not influenced by the waving 
movements of the stratification. 
The variation of the co-efficient of refraction 
according to the season. 
The two tables on pp. 156—157 and p. 162 of the levellings under- 
taken, are divided into three sections corresponding to the periods 
May 31st to June 22nd, July 9th to August 12th and August 23rd 
to October 21st. This division corresponds fairly well with three 
seasons, each with its own climatic peculiarities: the period of the 
melting of the snow, midsummer and autumn. It is therefore to 
be expected, as will by the way appear directly from the tables, 
that the conditions of refraction within each of these periods must 
show a definite tendency. 
In the summary below I have given the mean value of the co- 
efficient of refraction for each of the three periods. Besides I have 
in the case of the lines of vision at the cairns IX and X given the 
mean value of r (the rise of temperature per metre) for the inter- 
vals 5m to 200m and 5m to 500m. These mean values of 7 are 
computed from the results of all the kite- and balloon-ascensions 
within the period in question. The number of single values, on the 
strength of which the mean value of г has become determined, is 
given in a special column. In the case of the line of vision at the 
“Skerry” I have not made a similar computation of 7. The reason 
of this is that the observations of temperature on the ice and in 
the crow’s nest were only undertaken one day and night in the 
course of every month, during which day and night observations 
were made every second hour. It is therefore possible that the 
conditions on the day and night in question may have been ab- 
normal, so that a comparison between 7 and k might be quite mis- 
leading. However a cursory examination shows that this would 
hardly have been the case.!). 
It appears that there is a certain harmony between the manner, 
1) See: Die Temperatur in der Ausguckstonne am Grossmast der “Danmark” von 
W. Branp, Medd. om Grønland XLII. As to the series of observations 
July 17—18 1907 the mean value of the inversion has by a misprint been 
given as —- 1.1° C.; it should be — 1.19. 
