444 I. P. Косн. 
tunnels of splendid ice arcs, through which the river flows. Under 
particularly favorable conditions the tunnels assume the shape of 
extensive ice grottoes, the gorgeous splendour of which suggests fairy 
land. The phenomenon is exhaustively described and illustrated in 
the present volume, “Die glaciol. Beobacht. d. Danmark Exp.” chaps. VI 
and VI. 
The existence of the small lakes is analogous with that of the 
rivulets. In the month of June, when the country is strongly heated 
by the steady and powerful solar radiation, the melting of the ice 
progresses rapidly. At the end of June and the beginning of July 
Fig. 138. Rivulet. Danmarks Havn. July. 
the ice has disappeared, and the lakes and bogs now form a favourite 
resort of a great number of aquatic fowl. Already at the end of 
August the freezing begins, and from September the lakes are frozen 
over. 
One might be tempted to believe that the small lakes would 
very easily freeze to the bottom, because the ground round and 
under the lakes must have a temperature, which is several degrees 
below zero, and this circumstance occasions a cooling off of the water 
from below. The measurings available of the thickness of the ice 
on the lakes do not offer sufficient hold for an estimation of the 
matter, whereas one may get some information from the conditions 
in a small lake near the harbour of the ship, where for some time 
we went to fetch water. The greatest depth of water in the lake is 
