146 HYDROGRAPHY. 



Through the foregoing reflections, we thus come to the conclusion that the ice-water east of 

 Iceland is forming a Polar-current On account of its extent, and its being in the vicinity 

 of Europe, this Polar-current must have a great and decisive influence on the climate 

 of Northern Europe, and in consequence of its specially biological conditions be of 

 great importance for the fauna of the seas of Northern Europe. 



THE QUANTITY OF NITROGEN ABSORBED IN THE SURFACE-WATER. 



c — a is on the chart, plate XXXIV, placed iippermost on the right side of the small circle 

 that indicates the place of the station; c — b is placed on the right side of the nethermost part of the 

 circle, while the number of the station is found on the left side of this circle; e means the amount 

 of nitrogen found, expressed in c.cm. per litre of sea-water; a is the amount of nitrogen, which, ac- 

 cording to Hamberg, the water should contain to be saturated under a pressure of 76o mm and at the 

 temperature and salinity for the time being; b the amount of nitrogen which the water would contain, 

 if it had been saturated at the found height of barometer, temperature of water, and salinity, c — a and 

 c — b are thus two expressions for the supersaturation of the water with nitrogen. 



Casting a glance on the ciphers marked on the chart, our attention will at once be attracted 

 by the fact of large areas of the surface of the sea being supersaturated with nitrogen, even to a 

 pretty high degree. It will be seen that this is specially the case with the stations that are lying in 

 the Arctic-sea water north-east and east of Iceland, and it must furthermore be pointed out with re- 

 spect to these stations, that in the uppermost strata of water there has been a very quick falling of 

 temperature with the depth. Thus the supersaturation at the stations 106 and 107 is roo ccm , but at 

 the same time it will readily be perceived that while the temperature at the surface is about 6°, it is 

 already at a depth of 20 fathoms (57 metres) coming down to o°6 and — i°i. This supersaturation 

 with nitrogen proves that the warm surface-layer north and east of Iceland is due to a 

 hasty heating of the surface of the sea by the atmosphere and the sun, which likewise 

 is implied by the low degree of salinity. The inference might of course also be drawn that the 

 existence of the warm surface-layer was due to the afflux of warm water from warmer tracts of the 

 sea; but however likely such an assumption might be, it is entirely out of the question here, as in 

 that case, the supersaturation could not be accounted for. 



The blue cipher in the chart shows how much the temperature is higher at the surface than 

 at a depth of 20 or 30 fathoms (38 or 57 metres). Where this cipher is high, or, what here must be 

 considered as synonimous with it, where a quick heating has taken place, we shall also meet with 

 an ample supersaturation. As it can be seen, the difference between the surface temperature and that 

 at a depth of 20 — 30 fathoms (38 — 57 metres) is here put down as a measure for the heating. It must 

 be admitted thas this mode of proceeding is not quite correct, for the exact measure can only be 

 ascertained by observing the temperature of the same water at different times, but as I had not at 

 my disposal a series of observations of this kind, I had no other choice than having recourse to the 

 aforesaid measure, which under all circumstances has to be used with discretion. 



