ON THE COASTS OF IRELAND. 



33 



Station. 



Apparent 

 Mean Height 

 with de- 

 creasing 

 declination. 



Apparent 

 Mean Height 

 with in- 

 creasing 

 declination. 



Excess of Apparent 

 Mean Height with de- 

 creasing declination 

 over Apparent Mean 

 Height with increa- 

 sing declination. 



ft. 



+ 0-01 

 + 0-10 

 + 0-02 

 + 0-20 

 + 0-01 

 + 0-03 

 + 0-48 

 + 0-24 

 + 0-20 

 + 0-25 

 + 0-27 

 + 0-23 

 + 0-14 

 + 0-14 

 + 0-13 

 + 0-12 

 + 0-06 

 + 0-11 

 + 0-24 

 + 0-16 

 + 0-08 



It would seeiih from this that, if the apparent mean height depends upon the moon's 

 declination, it is greatest when the moon's declination has decreased nearly to the 

 point where the argument of declination is 135° or 315° (which makes the declina- 

 tion =— ;=x maximum declination). Thus at the middle of the observations, it is 



greatest about July 22. Now on July 22, the magnitude of the tide, though above 

 the mean, was not maximum. From this circumstance, and from the decided supe- 

 riority in magnitude of the excess found by classifying the tides by the moon's decli- 

 nation, over the excess found by classifying the tides by the magnitude of the tide, 

 it appears extremely probable that the excess does really depend on the moon's de- 

 clination. In that case, the greatest apparent mean height will occur about four 

 days after the day of greatest declination. 



Section VI. — Discussion of the range of tide; and of semimenstrual inequality in height, 

 apparent proportion of solar and lunar effects as shown by heights, and age of tide 

 as shown by heights ; from high waters and from loiv waters. 



The numbers from which we shall extract the results of this section are contained 

 in the table of page 30. The means of the heights are made subservient to the 

 accurate determinations of specific heights in the following manner. If & is the dif- 

 ference of right ascension of the sun and moon, S and M their respective single 

 effects, then (neglecting declinations, &c.) the actual height may be represented by 



If we expand this and integrate from ^ = — 45° to 



A+Mv^<|l+^cos2^+— ^ 



Wf 



MDCCCXLV. 



