532 



REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



[8] 



Sea tends to mix the waters. The following figures are the result of 

 actual observations : 



List. 



ISLAND OF SYLT. 



Surface water: 



Specific ■weight. 



Per cent, salt 

 Bottom water: 



Specific weight. 



Per cent, salt ... 



WILHELMSIIAFEX. 



Surface water: 

 Specific weight. 

 Per cent, salt ... 



Bottom water: 



Specific weight 

 Per cent, salt . . . 



HELIGOLAND. 



Surface water: 



Specific weight. 

 Per cent, salt ... 



Bottom water : 



Specific weight. 



Per cent, salt 3. 35 



OUTElt LIGHTSHIP, IHVF.U WF.SER. 



Surface water: 



Specific weight. 



Per cent, salt ... 

 Bottom water: 



Specific weight. 



Per cent, salt . . . 



1. 0208 

 2.72 



1. 021C 

 2.82 



1. 0203 

 2.66 



1. 0205 

 2.69 



1. 0188 

 2.46 



1.0215 

 2.82 



1. 0203 

 2.66 



1. 0205 

 2.09 



The annual average saltness is therefore much more uniform at every 

 jflace above mentioned than in the Baltic. The occasional fluctuations, 

 especially the lower figures, are caused by a large influx of fresh water, 

 and they consequently occur more frequently in surface than in deep 

 water. If the water at times is heavy, this is a sign that water from the 

 ocean has entered the North Sea, whilst if it is light, it shows a consid- 

 erable influx of river or Baltic water. The same influences are at work 

 as regards the remarkable temperature of the North Sea. 



The southern part of the North Sea resembles the Baltic ; it is shallow, 

 and its nearest communication with the ocean is a narrow channel. In 

 this part of the North Sea the temperature of the water, like that of the 

 Baltic, is controlled by the temperature of the air. The only perceptible 

 differences are caused by the influx of warm water from southern lati- 

 tudes through the channel and by water from the rivers Weser and 

 Elbe, as well as by water from the Baltic, varying in its temperature 

 according to the seasons, entering the North Sea. 



The central part receives water from the south and north at a greatly 

 varying temperature during the course of the year. In summer the 

 surface water coming from the south, from rivers and from the Baltic, 

 is warm, whilst the water from the north, passing by and over shallow 

 places, is cold. In winter this condition of things is reversed, as the 

 shallow southern part then grows cold j the same applies to the Baltic 



