Survey of Northeast Greenland. 229 
Station XII 
Altitude of telescope 63.0 m — 1.0 m — 64.0 m. 
Gain nic III V VI VII VIII IX x M 
ae 9021841” 89°52’36” 88°10’30” 88°43'13” 88°41’44” 89°19'32” 88°40'05” 9092510" 
в 1.7 5.9 50.0 2,3 133 5.8 15.3 2,1 
curvature 
Altitude ..... 38.3 89.9 977.2 195.3 396.2 178.2 428.1 26.1 
Station V 
Altitude of telescope 88.0 m + 1.4 m == 89.4 m. 
Gain... VI VII VIII IX xX XII M 
Ben... 87°17'40” 89926709” 88933708” 3994517” 89914708” 90912709” 90°43'30” 
Altitude. 968.3 194.5 395.1 178.0 425.7 62.5 24.5 
Station VIII 
Altitude of telescope 394.0 m + 1.4m = 395.4 m. 
Cairn, .. V VI VII IX x XII 
[VMS 91°32'24” 88°23'32" 91218397 9025731" ‘8995823 91924'36” 
Altitude. 89.8 970.2 195.1 176.9 497.1 63.9 
Station X 
Altitude of telescope 426.0 m + 1.3 m — 427.3 m. 
Cairn... V VII VIII IX al 
DER ОМ 9025621” 91205725” 90910718” 92°20'38” 92°17'23" 
Altitude. 91.6 195.7 395.2 rio 132.3 
The difference between the altitudes computed for the same 
point might, as it will appear, sometimes become rather considerable, 
as far as the points in the base network are concerned up to about 
1 metre, as far as the other points are concerned up to about 2 metres; 
the points V and VI, however, showed differences of as much as 
4.5 т and 8.9m. These deviations, as mentioned above, are mainly 
due to changing conditions of refraction. When fixing the final 
values no mean was, therefore, computed; I took it for granted that 
the levellings on the shortest distances ought to be the best, but 
otherwise I made allowance for a possible uncertainty of the pointing. 
An uncertainty of this kind nearly always arose in the case of 
downward sights, in that the background was then, as a rule, un- 
favourable. 
A striking fact is that all the levellings from Station XII give 
too high values. This might indicate peculiar conditions of refraction 
on the day in question. 
If we take it for granted that the error dH' on the altitudes 
computed from a single station is exclusively due to the error dk 
of the refraction constant, we get, by a simple differentiation of the 
formula given on p. 227: 
Е У 
dH’ — акр» or dk = + dH’ >, 
