Survey of Northeast Greenland. 171 
Refraction conditions in the line of vision Observatory— 
Ра, 
——щ——ыЫыЫыыЫы—ы———0—Ы—ЫыЫ—Ы—М—Ш—Ш—Ш—шШшШшШ— 
|| 
Date | Hour | oy [rx+003%42| т; | x | 4 Ak 
19, Aug 22 8230 | 746.5 | 0.0391 | 2784 | 0.254 + 0.020 | + 0.176 
Mers RTE 8200 | 754 0.0433 2746 | 0.293 | + 0.059 | + 0.044 
И TO | 756 0.0331 | 272.6 | 0.227 | -= 0.007 | — 0.056 
8. Sept. .... | 2250 | 744 0.0385 | 271.8 | 0.262 | + 0.028 | -= 0.068 
Wie ete. 10500738 0.0271 | 269.0 | 0.186 | -= 0.048 | -- 0.126 
| RES 9230 | 738 0.0307 | 270.7 | 0.209 | -: 0.025 | - 0.040 
15. — .... | 3590 | 745 | 0.0343 | 266.1 | 0.244 | + 0.010 | +0.090 
mee 2p50 | 742 0.0253 268.4 | 0.176 | -= 0.058 | —0.044 
10 Det: |... 1250 | 737 0.0283 | 259.9 | 0.208 | 0.026 | + 0.035 
21. — .... | 1730 | 155.5 | 0.0873 | 2578 | 0.286 | +0.052 | + 0.148 
Mean... | 0.234 | -- 0.003 
By putting k'X = 0.003 — 0.234 one may, on the strength of 
this, get the mean value of the co-efficient of refraction for the sight 
‚Observatory—Cairn IX for the period May 31st—October 21st. It is: 
See ene 
kX — 0.237 
where the second decimal may be supposed to be reliable. The great 
difference between the values of 4x and 4k is a fact for which, as 
mentioned above, one must be prepared. It is a striking fact that 
whereas 4x oscillates between — 0.059 and - 0.058 dk oscillates 
between + 0.176 and — 0.126. Similar conditions though not quite 
so marked we shall find at the lines of vision at Cairn X and at 
the „Skerry”. The cause of this we will treat later on. 
In the table given below (p. 173) of refraction conditions in the 
line of vision Observatory—Cairn X no mention is made of the 
conditions on September 11th, because, on that day, the kite only 
reached an altitude of 200 ın. As kr is determined at 0.160 I have 
not formed the values 4x and have, instead of 4k, given К as deter- 
mined by К = 0.160 + 4k. At the computation of the means it 
has been necessary, on account of the too abnormal conditions, to 
leave out the figures given in brackets for October 21st. In order 
to show the justice of not including the values of that day in the 
means, I shall quote — from WEGENER’s above-mentioned “Drachen- 
und Fesselballonaufstiege’’ — the result of the ascension of kites on 
that day. 
With the colossal inversion of 10.9 to 11.2 degrees between 200 m 
and 500 m (at 1P18 to 1P48; see below) it is quite natural that we must get 
an abnormally high value of xx, and to this should correspond a simi- 
lar abnormally high value of k. On this day we also get the highest 
