Survey of Northeast Greenland. 131 
of the instrument is left out, the error of the zenith point with its 
full value will enter into the latitude as shown on Fig. 6, in which 
manner the following result is arrived at 
Le РаПе, — 20-9 
It is а matter of course that besides the microscopes of the 
vertical circle the level of same must be read off with every observa- 
tion, in order that all the readings of 
the circle may be reduced to the same | 
reading of the level i. e. to the same : 
zenith point. S | O N 
In view of the computation of the 
refraction the pressure of the air as 
well as the temperature have to be ob- 
served. 
Stars, the zenith distance of which 
exceeds 50°, ought not to be used. 
Under favourable conditions one may 
in the course of a single night make as Fig. 6. 
many as fifty observations, and with a 
good instrument the latitude may in this manner be determined 
with a mean error of about 0”.2. The high arctic conditions are, 
however, not favourable; one becomes comparatively quickly indis- 
posed, and it pays, therefore, to extend the observation over several 
occasions. 
Especially in the course of the determinations of latitude, it was 
principally felt as a very serious drawback that we had not at our 
disposal a larger star catalogue than the Nautical Almanac. As 
early as the month of November the temperature became so low 
that conditions were unfavourable in cases where the utmost 
accuracy was aimed at. We had to profit by the moonlight nights 
during the months of September and October 1907 for the purpose 
of making determinations of longitude; several nights offered no 
prospect, owing to a cloudy sky or bad weather, and consequently 
we had only a few nights left for the determination of latitude and 
the investigation of the astronomical refraction (see pp. 136—147). 
The preparations to be made for the observation are 
exceedingly simple. They consist in determining the meridian point 
of the horizontal circle, in selecting suitable stars from the catalogue 
and in making a list of the approximate clock times and of the 
zenith distances corresponding to the culmination. The observations 
81x 1907 are given below. Each microscope is read off on both 
