^52 



HYDROGRAPHY. 



Passing in review all these observations, the inference may be drawn that in 

 the tract of the sea, from 15 — 20 Long. W., a line of demarcation may be drawn be- 

 tween the bottom water that has come across the Faroe-Iceland ridge in a southerly 

 direction, and the rest of the bottom water farther to the westward in the Atlantic, 

 which latter therefore must be supposed to originate from some other sources, and furthermore that the 

 results gained through the analyses of nitrogen, are not at any point in contradiction 

 to the conclusions already drawn, but even supplement and corroborate these 

 latter. 



ON THE OTHER DETERMINATIONS OF NITROGEN. 



At station 71, the difference between the actual temperature and the temperature of absorption 

 is found to be o°6 at the surface, — o°2 at a depth of 40 fathoms (75 metres), that is to say, there is 

 a supersaturation at the surface, and an incomplete saturation at the indicated depth. This confirms 

 the correctness of the assumption that the water is coming from the southward, consequently from 

 warmer to colder regions of the sea, and the cooling of the water that is due to this circumstance, has 

 the effect of making it incompletely saturated. At the surface the increasing heat of the summer may 

 however, give rise to a slight supersaturation. At station 89 there is a slight supersaturation at a 

 depth of 30 fathoms (57 metres); this is probably due to heating from the surface, as it can be seen 

 from the curve that the temperature, below the aforesaid depth, suddenly goes down i°. The observa- 

 tions at station 94 show throughout incomplete saturation, and specially at a depth of 30 fathoms 

 (57 metres), which very likely may be attributed to a great cooling from above, originating from the 

 cold ice-water. 



At station 101, we find at a depth of 30 fathoms (57 metres) incomplete saturation. It is 

 obvious when looking at the curve of temperature, that at this place the temperature is rising with 

 the depth, a circumstance which is due to the fact of the warm water that is coming from the west- 

 ward from the Irminger Current having been cooled by the ice-water that is lying above it On the 

 other hand, a great supersaturation is prevailing at a depth of 100 fathoms (188 metres). There is 

 every reason to believe that this is due to observational errors, but on account of the amount of 

 oxygen being great too, we cannot take it for granted that this is the case. But now it is seen, 

 however, that the degree of salinity is specially low (33'6o), and the temperature rather high, which 

 is a state of matters that will have the effect of producing an unstable equilibrium. This is a sign 

 of the ice-water having made its way downwards and got mixed with the warm water below from 

 the Irminger Current. Provided that this assumption be correct, the supersaturation cannot be ac- 

 counted for. As according to this, the observations we have before us are at variance, I think it is 

 not unlikely to be supposed that the water bottle also has fetched up water from a smaller depth 

 than 100 fathoms (188 metres). At station 102, there is an inappreciable supersaturation at a depth of 

 20 fathoms (38 metres). It will be seen that this spot is located on the first downward bent branch 

 of the temperature-curve; the water at the said depth has consequently been subject to heating, 



