Survey of Northeast Greenland. 195 
of the same kind as the outline of the country and must be supposed 
to be caused by the fact that the line of vision passes quite closely 
across the country. 
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2 % 
Fig. 21. Telescopic image of Horizon Ш, on October 21st at 9230. 
Fig. 22 shows a commonly occurring case of a false sea horizon, 
caused by а downward mirage over open water. Owing to the wave 
movement of the water the false horizon is rather uneven. The 
movement in the reflecting stratum of air has the effect that in the 
reflected image of the celestial vault under Horizon II one may catch 
a glimpse of the constant shifting of small wave crests, which seem 
to leap up from the false horizon, in order to subside immediately 
afterwards. The real horizon is just perceptible at solitary small 
floes in the water. At Horizon I, where a number of small icebergs 
Fig. 20. Telescopic image of Horizon I (to the right) and Horizon II 
on August 12th at 9P00. 
are gathered together, it was possible to point the real sea horizon. 
The difference between the zenith distance of the latter and the false 
horizon was here measured at 40”. 
Fig. 23 shows a simultaneous downward and upward mirage’). 
of In i 
ih INN 
Fig. 23. Horizon II, double mirage on September 11th at 9240. 
The three small bits of calving ice clearly show the downward 
mirage. An observation of the zenith distances gave the following 
result: 
') The kind of upward mirage PERNTER (Meteorologisehe Optik), in the case of the 
sea horizon calls “Erhebung des Horizontes”; for the icebergs at the horizon he 
would presumably in this case use the designation “Verticalverzerrung”. 
