18 



Waters inside Skagen 



the mean height of the spring-tide 



Slipshavn 1 fool 



Helsingor „ 5 inches 



Copenhagen . . . „ — 7 — 



The North Sea and Skagerak 

 mean high-water above mean low-water 

 Thyboron channel . . 1 foot 6 inches 



Agger 1 - 1 — 



Hirshals 1 — „ — 



Skagen 1 — „ — 



The figures for the places inside Skagen are so small that they are often 

 neutralized by the change of level caused by the winds. The wind's influence on 

 the height of the water-level is at many places very distinct and well known. 

 Thus, westerly winds cause a high level of the water in the Kattegat on account 

 of the influx of water from the Skagerak , while easterly winds cause a low level 

 of the water. With the variable winds, so pronounced in our country, the changes 

 in the level of the sea are also very variable; but as certain directions of the 

 wind are predominant at certain seasons, others at other seasons, the average height 

 of the water-level is also ditterent at different periods of the year. From Adam 

 Paulsen a general summary is given here of the average deviations of the water- 

 level at three different places on the Danish coasts from the height of the mean 

 water-level during the twelve months of the year, calculated as the averages of 

 observations made during the years 1889 — 1902 



The annual variation of the, height of the water-level. 



Station 



Jan. 



Febr. 



1 



March 



April 



May 



June 



July 



Aug. 



Sept. 



Oct. 



Nov, 



Dec. 





cm 



cm 



cm 



cm 



cm 



cm 



cm 



cm 



cm j 



cm 



cm 



cm 



Frederikshavn . 

 Fredericia 



-0,3 

 1,2 

 (),G 



~4,(] 

 4,7 

 -2,7 



- 8,8 

 ^-7,4 

 —4,5 



-10,8 

 11,6 



— B,« 



-10,7 



- H,6 



- .5,4 



2 2 



-2,fi 



5,2 

 .3,9 

 1,3 



7,2 



5,5 

 2,8 



8,8 ' 



6,(; 1 



5,1 1 



6,6 

 6,7 

 6,0 



3,7 

 5,3 

 3,4 



6,6(4) 

 7,3(5) 

 2,6(2) 



The numbers in parenthesis for December indicate the annual mean-height of 

 the water during this month, when the extraordinary mean-height for December 

 1898 is left out of consideration. 



It appears from this, that the lowest water-level at all three places is in April, 

 and it is in agreement with this, that easterly winds according to simultaneous 

 observations are most predominant in April. This condition is of the greatest im- 

 portance to the upper littoral vegetation, and it is the reason why an upper belt 

 of vegetation, which has grown perfectly well during the course of the winter, is 

 killed every spring. 



Division of the Danish waters. To facilitate the summary over the di- 

 stribution of the Algae, I have not only maintained the ordinary divisions, but have 

 also made further subdivisions in the Kattegat and Baltic. These will be found 



' Adam Paulsen, Meddelelser om det danske meteorologiske Instituts Vandstandsmaalinger. (Ac- 

 count of the measurements of the height of the sea-level, carried out by the Danish Meteorolog. Insti- 

 tute. Nautisk-Meteorologisk Aarbog 1906, Kebeniiavn 1907. 



