Survey of Northeast Greenland. 259 
Souchier's distance meter — of which the expedition carried 
two — was only used by HAGEN and myself. It can easily be carried 
in the pocket, cannot get out of order and does not cost much, but 
measuring with it requires some 
practice and cannot be performed С» С, 
under all circumstances. 
Souchier’s distance meter con- 
sists of a glass prism of the shape 
indicated in Fig. 35. 
For protection the prism is 
enclosed in a covering of celluloid 
or ebonite, except the pieces AF 
and DC H. Above the latter spot 
a slide is placed, so that when 
sighting through DC one may cover 
СН and vice versa. 
Suppose the point at which 
the distance is to be measured to 
be G; the point is supposed to be 
so far off that the two rays of 
light Gm and Gn may be considered 
parallel. If one looks through the 
plane CH, G will be visible in the 
direction G,, which deviates 90° 
A 
Fig. 35. Souchier’s distance meter. 
from the original one; if on the other hand one looks through the 
plane DC, G will be visible in the direction G,, which with the 
direction at G, constitutes an angle of about 1°10’. 
The principle underlying the use of the instrument is as follows: 
A 
В. 
Fig. 36. 
One sights through the plane DC towards G, 
which is supposed to be visible nearly in 
the direction towards $ (Fig. 36). One shifts 
backwards and forwards and laterally, so 
long until one finds in the terrain a remote, 
sharply defined point S, the picture of 
which coincides with the picture of G. The 
standing place À is marked off with a stick, 
and the observer moves backwards in the 
prolongation of SA, until through the plane 
СН he sees G in the direction BAS. 
Thus one gets the distance looked for: 
b 
d = == 50D: 
sin 1°10’ 
