ON THE COASTS OF IRELAND. 



115 



From Mullaghmore to Port Rush, the second wave appears to travel with the 

 same speed as the principal wave. In passing through the narrow channel to Glen- 

 arm, its phases appear to increase much more rapidly than those of the principal 

 wave; or, it appears to travel more slowly, or in the opposite direction. This how- 

 ever is probably only an instance of the forced progression of the phases of wave in 

 the channel connecting two tidal seas. 



The general relations however of the waves depending on 2p at the different littoral 

 stations will be seen more clearly from the following process : — Take the establish- 

 ment of each station from Section XII I., and convert it into degrees at the rate of 

 1440° for a tidal day, and subtract the angle thus found from the angle added to 2p. 

 It is evident now that our phase j»' at every station is referred to the same origin, 

 namely to the time of the moon's transit at Greenwich. The expressions thus ob- 

 tained for the quarto-diurnal waves are the following: — 



Station. 



Large tides. 



Kilbaha .... 

 Casleh Bay . . 

 Galway .... 

 Old Head . . 

 Mullaghmore 

 Port Rush . . 

 Bally castle . . 

 Glenarm .... 



|ft. 



0-l6.sin(2y + 

 0- 16. sin (2/)' + 

 0-18. sin (2/?' + 

 0-08.sin(2/>' + 

 0-06. sin (2/ + 

 0-08. sin (2/j' + 

 0-07. sin (2y + 

 0- 17. sin (2/ + 



244) 

 235) 



223) 

 208) 



Small tides. 



Station. 



ft. 



0-08 



0-07 



0-08, 



0-04, 



198)|0-04. 



113)0-04. 



203)0-06, 



156)0-05, 



.sin(2y + 295) 

 sin(2/>' + 296): 

 sin(2/>'4-277)j 

 sin (2/ + 278) 

 sin(2j9' + 263): 

 sin(2jo' + 190) 

 sin (2/ + 245)1 

 sin (2/+ 147) 



Donaghadee . . 



Ardglass 



ClogherHead. . 

 Kingstown .... 

 Dunmore East . 

 Passage West . . 

 Castle Townsend 



Large tides. 



Small tides. 



ft. , ft. 



0-07.sin(2/>'+ 122) 0-03, 

 0-18.sin(2jo' + l63)|007 

 0-26.sin(2y + l67)|0-13 

 0-38.sin(2/9'+ 195) 0-23 

 0-14.sin(2y+ 72)0-11 

 0-29. sin (2/ +344)10-24 

 0-21. sin (2/)'+ 7)'0-l6 



sin 

 sin 

 sin 



(2/+ 41) 

 (2^+199) 

 .o..i(2/ + 218) 

 .sin(2jo' + 235) 

 .sin(2/>'+ 71) 

 .sin(2jo'+ 10) 

 .sin(2/?'+ 27) 



The expressions for Courtown, the station intermediate between Kingstown and 

 Dunmore East, are (as I remark by anticipation from the next section) intermediate 

 between those for Kingstown and Dunmore East, but nearly coinciding with the 

 former. 



The variations in the values of the constants attached to 2/? in the Table of page 

 113, seem to make it impossible for us to attribute this term to the local circum- 

 stances of each port, and the consideration of the Courtown tides in the next section 

 will confirm this. The order of the numbers attached to 2// in the last Table shows 

 that it may be considered as a progressive wave, beginning at Kingstown nearly, and 

 travelling both ways round the coast as far as Donaghadee. But whether such a 

 thing is mechanically possible, or whether it can be true that the quarto-diurnal wave 

 (which necessarily is created by the semidiurnal wave flowing over the shallower 

 seas between Ireland and Cornwall) can show itself as a great swell opposite Kings- 

 town, and can then be propagated even opposite to the semidiurnal wave and round 

 the island, are points which I cannot explain. 



On the whole, I am not able to pronounce with any confidence on the origin of 

 this wave, but I have no doubt that, having been created, it travels along indepen- 

 dently, and therefore that its existence is not due to the local circumstances of the 

 several stations. 



q2 



