Survey of Northeast Greenland. 
153 
a FE Så Degree 
| Temperature |Baro-| of z,t+z 
Date Hour > meter, mols сы 2, Le т 1809 k 
| | ture | + 
ros See ee ae oe anes 4 
11. Aug. 1935 | + 8.0! --9.0 757 | 4910| 6917750”.9 | 93°10'43”.9 | 86°52’53”.0 | 216”.9 | 0.102 
11. — 2P55 | + 9.5 | + 8.8—9.6| 756 | 44 07.2 04.9 57.7 | 182.6 | 0.244 
24. — |2а40|- 28| +20 760 | 87 43.5 | 26.5 | 43.0 | 189.5 |0.217 
SON 27 00 | 760: | 106 68.3 50.1 | 41.8. | 211.9 |0.124 
27. — 10р351- 2.2; - 3.3 763 | 64 28.3 | 24.3 56.0 | 200.3 10.171 
в PAO 37) 3.0 | 763 | 68 169 | TN 60.8 | 198.5 | 0.178 
9. Oct. |Op10 + 10.3| —9.3 | 757 | 82 | 51:50! 33.3 41.8 | 1951. 10.199 
9. — [1920 | 10.1 | ==. | 707 ar 45.1 | 32.6 47.5 | 200.1 ‚0.172 
Mean... |86°52°50".2| (0.175 
be natural. The greatest variation in z, on a single day occurs on 
August 11th; the difference between the two values of z, is here 39”. 
The meteorological conditions during the first series of observations 
on the above-mentioned day at 1P35 are given in the example on 
p. 151. During the second series of observations at 2P55 the obser- 
vation journal shows that the wind changed from WNW to SE, and 
at the same time the temperature fell quite suddenly from + 9.6 to 
+ 8.8. Besides the observation journal mentions haze and glimmer. 
The atmospheric conditions on this day have thus been rather un- 
settled, and consequently there is nothing strange in the fact that 
the co-efficient of refraction should vary a great deal. However, it 
is quite obvious on the very face of it, that in case the difference 
Z, + 25 is subject to such great and sudden variations, one cannot 
attribute any high degree of accuracy to a mean of eight determina- 
tions of k, by means of reciprocal, simultaneous observations. 
ihe Observatory the Skerry'. 
То J. P. Jacobsens © (see the map, scale 1: 100,000 of Danmarks 
Havn and Environs, PI. П) which in the following will be called the 
“Skerry”, as in the case of Cairn X a large number of zenith distance 
observations were made, in order to determine the variation of the 
co-efficient of refraction. In order to make an absolute determination 
of the co-efficient of refraction above water, we erected on the rocky 
knoll of the “Skerry” — the top of which was otherwise used as a 
sighting point, and the altitude of which above the sea was 16.4m — 
a stanchion with a similar wooden disc as the one mentioned in the 
case of Cairn X. The small universal instrument was put up beside 
the stanchion on the same solid tripod which had been used at 
Cairn X. The position of the rocky knoll on the “Skerry” was 
determined by triangulation, and the necessary elements for con- 
