HYDROGRAPHY. 



153 



which, as we know, has the effect of producing a supersaturation. It is for the same reason that we 

 meet with a supersaturation at station 104 at a depth of 20 fathoms (38 metres), while, on the contrary, 

 the incomplete saturation at the same station, and at a depth of 30 fathoms (57 metres), must origi- 

 nate in water from this depth belonging to the lower stratum of water, the upper part of which has 

 been cooled by the ice-water that is lying on top of it. It is for the same reason that at station no 

 we meet with an incomplete saturation at a depth of 30 fathoms (57 metres); the same applies to sta- 

 tion in at a depth of 40 fathoms (75 metres). When the observations at station 112, at a depth of 

 100 fathoms (188 metres), show a supersaturation, the cause of this state of matters is perhaps due to 

 the whole of the stratum of water below the ice-water originating in Atlantic-water. The observations 

 at station 1 18, at a depth of 50 fathoms (94 metres), show that the water contains such a quantity of nitrogen 

 that the analysis scarcely can be supposed to be correct; furthermore the extraordinarily low percentage 

 of oxygen seems to be indicative of atmospheric air having exerted its influence on the determination. 



Looking at all the temperatures of absorption determined in the seas south and west of Iceland 

 through the analysis of nitrogen, it will be noticed that the temperature of absorption for water varies 

 but little at a depth between 40 (75) and 500 fathoms (942 metres), and remains between 6°2 

 and 7°9. Stations 72, 89, 97, and 99, at which the depth does not exceed 500 fathoms (942), have all a 

 temperature of absorption at the bottom of 6°7 or 6°8. The cause of this can quite naturally be ac- 

 counted for by the fact of the surface-water having been subject to cooling during the course of the 

 winter, in consequence of which it is sinking down till it reaches the bottom, or a colder and on ac- 

 count of this heavier layer of water. It is a matter of course that the water which is sinking to the 

 greatest depth, must be that which has been subject to the greatest cooling, and the temperature 

 of absorption for this water indicates thus approximatively the minimum tempera- 

 ture of the year for the place where the water left the surface. According to what has been stated, 

 the temperature of absorption for the said stations is 6°7 or 6°8, and this temperature should then accord- 

 ing to what has been explained above be the minimum temperature of the here described — or more 

 southerly — seas. 



Supposing a surface to be laid through all the bodies of water that have a temperature of absorption 

 of 6°7, it is evident that this surface must form the nethermost boundary of the vertical circulation of 

 water that arises in consequence of the changes of temperature the whole year round. The following 

 table has been made to facilitate the view of the position of this boundary surface. 



The Ingolf-Expedition. I. 2. 



