1903] Studier over naturforholdene i vestlandske f jorde. 43 



made, it has been found that in the By Fiord the temperature at 

 the surface in March sinks to 4 — 2° C. and rises in July and 

 August to 15—18° C. 



Exceptionally, the surface temperature may be as low as 0°, 

 and the absolute amplitude is supposed to be about 18° C. The 

 salinity at the surface is greatest in winter, and it rises in the By 

 Fiord to a little more than 33 pro mille. 



The lowest salinity noticed in the By Fiord has been 6.47 

 pro mille. 



The By and Herlø Fiords have occasionally been covered with 

 a layer of ice, but the Hjelte Fiord has never been frozen over. 



Observations have shown that temperature and salinity in the 

 latter fiord are not so low at the surface, as in the By Fiord. 

 Outside the mouth of the Hjelte Fiord is the Hellisø lighthouse, 

 where Professor Mohn several years ago took the temperatur es 

 at the surface of the sea. On page 22 the average temperatures 

 for the year, and its respective months, are given. The minimum 

 (4°. 5) occurs in March, the maximum (13°. 9) in August, the yearly 

 amplitude is thus 9°.4. 



In the By Fiord and the Hjelte Fiord (St. A, B), the yearly 

 amplitude cannot be exactly given, but it has, at any rate, been 

 made sufficiently clear that the difference in variation in temperature 

 and salinity is greater at St. A than at St. B, and it may without 

 doubt be stated as a general rule that the amplitudes in question 

 rise, the further one goes from the coast inwards in the fiords. 



Variation in temperature and salinity in the deeper layers of water. 



On pages 24 and 25 the conditions, in the Hjelte Fiord and 

 the By Fiord at various times in different years, are given. 



On page 26 will be found the differences between the highest 

 and lowest observed temperature and salinity values. From which 

 it is seen, that at depths of 50, 100 and 200 meters the variations 

 are greater in the Hjelte Fiord than in the By Fiord, exactly the 

 reverse of what was found to be case at the surface. 



With regard to temperature only, it will also be seen from 

 Pis. I and II that the temperature curves in the By Fiord expand 

 more towards the surface, and contract more towards the depths, 

 than is the case in the Hjelte Fiord. 



The principal cause of this is, in all probability, the difference 



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