438 Chapter VII. 



order to see whether all this brown dust is of a mineral 

 nature, and consequently originates from the land.^ We 

 found in the lanes quantities of algae like what we had 

 often found previously. There were large accumu- 

 lations of them in nearly every little channel. We 

 could also see that a brown surface layer spread 

 itself on the sides of the floes far clown into 

 the water. This is due to an alga that grows on the 

 ice. There were also floating in the water a number 



O 



of small viscid lumps, some white, some of a yellowish- 

 red colour ; and of these I collected several. Under the 

 microscope they all appeared to consist of accumulations 

 of diatoms, among which, moreover, were a number of 

 larger cellular organisms of a very characteristic appear- 

 ance.t All of these diatomous accumulations kept at a 

 certain depth, about a yard below the surface of the 

 water ; in some of the small lanes they appeared in large 



This dust, which is to be seen in summer on the upper surface of 

 almost all polar ice of any age, is, no doubt, for the most part, dust 

 that hovers in the earth's atmosphere. It probably descends with the 

 falling snow, and gradually accumulates into a surface layer as the snow 

 melts during the summer. Larger quantities of mud, however, are also 

 often to be found on the ice, which strongly resemble this dust in 

 colour, but are doubtless more directly connected with land, being 

 formed on floes that have originally lain in close proximity to it. 

 (Compare Wissensch. Ergebnisse von Dr. F. Nansens durchquerung von 

 Grotiland. Erganzungsheft No. 105, zu Petermanns Mittheilungen.} 



t I have not yet had time to examine them closely. 



