298 Prof. Nordemhiold — Expedition to Greenland. 



been continued, partly by tbe former Swedish arctic expedition, and 

 partly by Dr. Brown,^ during the voyages made by him in the arctic 

 seas as Surgeon in a whaler, and as a member of Whymper's ex- 

 pedition. We also endeavoured to divert the tedious monotony of 

 the voyage by observations on this phenomenon. 



The sea- water in the neighbourhood of Spitzbergen is marked by 

 two sharply distinguished colours — greyish-green and fine indigo 

 blue. In the Greenland seas we also find water with a very decided 

 shade of brown. These colours are seen most pure if one looks 

 vertically down from the ship to the surface of the water through 

 a somewhat long pipe. The green, or rather grey-green, water is 

 generally met with in the neighbourhood of ice (whence it was 

 supposed to arise from the arctic current) ; the blue where the water 

 is free from ice ; the brown, as far as I am aware, chiefly in that 

 part of Davis Strait which is situated in front of " Fiskernaes." 

 When specimens of the water are taken up in an uncoloured glass, it 

 appears perfectly clear and colourless, nor can one with the naked 

 eye discover any organisms to account for the colour. But if, when 

 the velocity of the ship allows of it (i.e. when the ship makes from 

 one to three knots an hour), a fine insect net be towed behind the ship, 

 it will soon, in the green and brown water, be found covered with a 

 film of in the former case green, in the latter case brown slime, of or- 

 ganic origin, and evidently the real cause of the abnormal colour of 

 the sea- water. Just in these parts may be found swarms of small 

 Crustacea, which live upon this slime, and in their turn, directly or 

 indirectly, become the food of larger marine animals. The blue 

 water on the contrary, at least in these seas, deposits no slime upon 

 the insect-net, and is far less frequented by Crustacea, Annelides, etc., 

 than the green. Thus, as Brown, in the article above referred to, 

 remarks, the presence of this slime, inconsiderable as it is, but spread 

 over hundreds of thousands of square miles, is a condition necessary 

 for the subsisteaee, not only of the swarms of birds that frequent 

 the northern seas, but also of that giant of the animal creation, the 

 whale, and all branches of industry dependent on whale-fisheries. 



Of these remarkable organisms Dr. Oberg collected specimens 

 when possible, during the voyage, which it is intended hereafter to 

 submit to a careful scientific examination, in conjunction with similar 

 specimens from preceding expeditions. Here we need only mention 

 that the slime itself in each particular place is formed only of a few 

 species of Diatomacea, often so large that after drying the mass, 

 the siliceous frustules may be discerned with the naked eye ; but 

 on the other hand, different parts of the ocean exhibit entirely 

 different forms, so that, for example, the green slime in one place 

 has sometimes not a single species identical with that in another. A 

 long continued collection will therefore be required to explain this 

 scanty but, nevertheless, so remarkable and, we may safely say, im- 

 portant flora of the ocean's surface. 



In Copenhagen our expedition was most kindly received by the 



' A very interesting essay on this subject has been published by Dr. Brown : The 

 Farmer, Jan. 1, 1868, p. 16. 



