D, 



INTRODUCTORY REMARKS. 



"uring my first visit to the East Greenland Sea in 1882, I noticed 

 that in the summer, when the surface of the ice-floes was much melted, it 

 got a very dirty and often brownish colour 1 . This was especially noticeable 

 on thick and very old ice-floes — what 1 call the real polar ice — which evi- 

 dently came drifting southward along the East Greenland Coast from very 

 high latitudes, probably after having crossed the then unknown sea near the 

 North Pole. 1 supposed that this dirty brownish colour was chiefly due to 

 dust from the atmosphere brought down on the ice by falling snow. To some 

 smaller extent 1 thought it might also be due to impurities or organisms in the 

 sea-water which had been frozen into the ice, and which were now aggregated 

 by the gradual melting of Ihe ice at the surface. During this voyage I also 

 noticed another feature, viz. that the thinner and comparatively new ice, one 

 or two feet thick was frequently coloured reddish brown on the under side' 2 . 

 By examination under the microscope on May 9, 1882, I found that the co- 

 lour was due to a layer of algae, chiefly diatoms 3 , adhering to the under- 

 side of the ice, f had, however, no opportunity, nor the knowledge then suffi- 

 cient to pay more attention to these highly interesting features. 



1 See "Naturen", vol. XI, Bergen 1887, p. 214. 



! This ice with a red underside was called "seal-ice" by the sealers, because they said 

 that the seal preferred to lie on floes of that kind. This might not be improbable; for 

 where there are so many diatoms in the water, there are probably also many Cru- 

 stacea, which form the food of the seal {Phoca groenlandica). 



3 According to the drawings I then made, the diatoms seem to have been Coscinodiscus, 

 Fragilaria, Navicula directa, and others. 



1 



