\Sg^. No. 9- HVDR.-BIOL. STUDIES OF THE NORW. FISHERIES 2l 



a 50 mètre layer oi North Sea water, and what is specially characteris- 

 tic of the Summer season are the conditions under which we find the 

 Atlantic Water. 



On comparing these with the results of investigations from other 

 seasons, it will at once be perceived that, during the Summer, tlie At- 

 lantic Water is to be found at a far greater height, much nearer the 

 surface than, for instance, during the Winter. The variation may even 

 amount to 150 or 200 mètres. The large amount of salineness of the 

 Atlantic water will be noticable. At Station Xo. i, we find that it 

 contains, even in such shallow depths as 120 mètres, the high saline 

 figure of 35.43 per 1000. 



It appears from the following, that these conditions, so peculiar to 

 the Summer-time, develope themselves Uttle b\- little during the Spring 

 (see PI. I, Fig. 2, i6th April', and that, during the Autumn, they change 

 to the widely different, but equally characteristic Winter conditions see 

 PI. I, Figs. 3. 4 & 5). PI. V, Fig. I, shews a section of the Christiania 

 Fjord. One may observe in it the great thickness of the Baltic layers, 

 and what is. moreover, an important matter is, that the Atlantic Water 

 does not reach the Christiania Fjord even during the Summer. 



The temperature conditions exhibit the peculiarity- of tlie tempera- 

 ture falling from the surface towards the bottom (PI. i, Fig. i b, from 

 15.6" on the surface to 6.5 " at the depth of 235 mètres). The tempera- 

 ture does not. however, drop evenly At a depth of between 60 and 

 70 mètres, we find the radius for 8 ", and it is especialh" striking that 

 the temperature from 45 to 60 mètres, or thereabouts, sinks from 13 " 

 to 9 °, thus no less than 4 degrees. If one compares Fig. i a, with Fig. 

 I b, both representing the same station, it is clear that the great fall in 

 the temperature occurs in the mixed layers, and that the warmer de- 

 grees of temperature are only to be found in the Baltic Current. On 

 comparison with other seasons of the year, for instance April (Fig. 2] 

 it will, moreover, be observed, that the warmth of the surface layers in 

 August have commenced to spread downwards, a condition which will 

 be subsequently seen continues throughout the Autumn. (See Figs. 3. 

 4 & 5). 



The Autumn. During the Summer and the beginning of Autumn, 

 the great afflux of fresh water from the rivers ceases. The Baltic 

 layers then become less, while, at the same time, the Bank Water in- 

 creases greatl}- in thickness (through a mixing of the North Sea water 



