[5] SCIENTIFIC EXAMINATION OF THE GERMAN SEAS. 529 



2. The surface water is invariably lighter, and contains less salt than 

 the deep water ; the difference between the two decreases in the direc- 

 tion from west to east. 



3. On an average the water is heavier and contains more salt in 

 autumn and winter than in spring and summer; this difference likewise 

 decreases in the direction from west to east. 



4. The variations of the specific weight and the saltness of the water, 

 that is, the differences between the tenqjorary variations of the water, are 

 also much more considerable in the west than in the east. Near Son- 

 derburg, and even near Kiel, the deep water occasionally contains so 

 much salt that it differs very little from the North Sea water in this 

 respect, whilst near Lohme, and still more near Hela, the heaviest water 

 contains little more than the average quantity of salt. 



As regards the second important condition of the water, viz, its tem- 

 perature, the Baltic shows the following phenomena : 



On account of its comparative shallowness, and because it cannot ex- 

 change its warmth with that of the oceanic water through wide open 

 channels, the temperature of the water of the Baltic will mainly be 

 regulated by the temperature of the atmosphere, and will in different 

 years be more or less dependent on the atmospheric temperature of those 

 years. As the water absorbs warmth slowly, and likewise cools off 

 slowly, the water will grow warmer or cooler somewhat later than the 

 atmosphere, and the deeper the water the slower will be this process. 

 The warmth and cold of the atmosphere will be the same in the water, 

 only it will occur later in point of time and will decrease in the direction 

 of the deep water. 



The temperature of the water, which is dependent on the local tem- 

 perature of the atmosphere, is somewhat changed by the currents. The 

 cold water, which in spring flows into the Baltic in enormous quantities 

 from the north and east, and which is chiefly produced by the melting 

 of the snow, creates a cold upper current flowing in a -westerly direction ; 

 and this current delays the warming of the water by the atmosphere, 

 and even tends to make the atmosphere cool (the cold days of May!). 

 The more or less powerful undercurrent from the North Sea will com- 

 municate to the deep water in the Western Baltic the warmth of the 

 North Sea water. As these undercurrents are strongest in autumn and 

 winter, and as the North Sea water is warmer during those seasons than 

 the water of the Baltic, the temperature of the deep water is raised as 

 far as the influence of these currents extends. 



The observations relative to this question made at the different sta- 

 tions show the following result : 

 S. Miss. 59 34 



