On Mean Sea Level and its Fluctuations. 



17 



to Gjedser ; of 259° at oui- Swedish ports ; of 277° at o\ir three German 

 ports in the Baltic. 



The cosine formuhTO of Table F. liive, on expansion, a very satis- 

 factory agreement with the observed results ; as is sliown. foi- instance, 

 in the following Table for Dundee (Fio;. 7). 



Table G. — Mean Monthly Values of Mean Sea Level, compared with 

 the Annual Mean, at Dundee (in feet). 



Observed . 

 Calculated 

 Difference 



Observed . 

 Calculated 

 Difference 



Mean, Hi'ih Water. 



•45 

 •39 

 •06 



•25 

 •27 



•02 



Menu Loiv Water. 



In all of these cases there are obviously other factors (though small 

 in amount) entering into the composition of the wave, and this is the 

 case in somewhat greater degree in the more irregular curves presented 

 by the foreign stations. But the following example is sufficient to' 

 show that a harmonic formula, including only an annual and a semi- 

 annual component, approximates very fairly well to the conditions of 

 the curves at the foreign stations also. 



Table H. — Mean Monthly Values of Mean Sea Level, compared with 

 the Annual Mean, at German Baltic Ports. After Kriimmel 

 (reduced to feet). 



It will be seen that the differences between the observed and 

 calculated values are, as nearly as pos.sible, of equal magnitude in the 

 case of Dundee and of the German observations. It is possible, or 

 even probable, that the differences might be eliminated, in great part 

 if not wholly, by taking into account other harmonic factors of com- 

 paratively long period, such as the tides Mf , MSf , and Mm. ; but it is, 

 of course, impossible to investigate these on the ba.sis of our twelve 

 monthly means. In any case they are not of sufficient magnitude 

 to obscure or invalidate the aimual and semi-annual waves, which 

 are the main features of the curves. 



