Survey of Northest Greenland. 101 
we came to possess a complete collection of examples of calculations 
for our guidance in Greenland, the value of which cannot be suffici- 
ently appreciated. The Danmark-Ekspedition owes a great debt of 
gratitude to Professor SCHNAUDER for the considerable and disintere- 
sted work which he undertook on our behalf. 
Determination of Azimuth. 
The Observatory formed part of the triangulation net, being used 
as a station. In this manner it was made possible to carry out the 
determination of azimuth for the orientation of the triangulation net 
from the Observatory itself. Cairn V which was situated in a direc- 
tion very nearly due south and at a distance of 16 km, could in 
this manner also serve as a meridian mark during the daytime, so 
that it was not always necessary to make a new azimuth observa- 
tion to determine the meridian point of the horizontal circle, when 
the instrument, for some reason or other, had been removed from 
the pillar. 
In determinations of azimuth we used the polar star. In lati- 
tudes as high as that of Danmarks Havn it is necessary to use the 
ocular prism in the case of observations of the polar star, because 
the zenith distance is so small. The observation of the star, there- 
fore, requires a small a priori calculation, which may, however, be 
made quite roughly. For the below mentioned observation the a 
priori calculation has probably been confined to the following: 
According to the sidereal chronometer the observation will take 
place at about 18h 30"; clock correction about + 1? 18", thus sidereal 
time, #, about 19:48; hour angle { = #4 = about 19h 48m = 1h26™ 
— about 185.4. During the observation the polar star will thus be 
very near its eastern elongation; its zenith distance must consequently 
be all but equal to the zenith distance of the Pole, thus for Danmarks 
Havn where the latitude  — 76°46’, z = about 13°.2. This is suffi- 
cient. The finder is adjusted at 13°.2, the telescope is by estimate 
directed into the vertical plane of the star, and it will then as а rule 
prove to be in the field or at any rate so near the latter that it is 
found immediately by carefully moving the instrument round the 
vertical axis. 
In the following example thread No. 3 has not been used as a 
middle thread, but the polar star and the cairn are pointed right 
between threads No.3 & 4. In this manner arises a collimation con- 
stant of about !/»’ (the interval between the threads is about 1’), and 
this in its turn yields the very obvious difference of 5' in the rea- 
dings of the polar star, corresponding to “telescope east” and “tele- 
scope west”. For “telescope east” and “telescope west” we took, as 
