48 The Piev. S. Haiighton on the Solar and Lunar 



One of these stations, Kih'ush, Co. Clare, was abandoned shortly 

 after the commencement of the observations, in consequence of 

 difficulties experienced in obtaining a sufficiently sheltered posi- 

 tion for the tide-gauge ; and at another station, Killibegs, Co. 

 Donegal, the observations made were not of so complete a cha- 

 racter as at the remaining ten stations. 



At the request of the Committee of Science of the Royal Irish 

 Academy, I imdertook the task of reducing and discussing the 

 tidal observations, the reduction of the meteorological observa- 

 tions being undertaken by the Rev. Humphrey Lloyd, whose 

 ' Notes on the Meteorology of Ireland,' deduced from those ob- 

 servations, have been recently published by the Academy. 



The tidal observations made under the direction of the Aca- 

 demy were of two distinct kinds : the first being the observation 

 of all the high and low waters at each of ten stations for periods 

 varying from sixteen to twelve months ; the second being the 

 observation of complete tides at intervals of fifteen minutes, the 

 tides selected for this purpose being four in each lunation, two 

 spring and two neap ; these observations were made at eleven 

 stations, and, like the former, extend over a period varying from 

 sixteen to twelve months. 



These two classes of observations were made for the purpose 

 of throwing light upon different questions connected with the 

 laws of the tides ; the first class of observations being intended 

 to furnish data for the separation of the effects of the sun and 

 moon in the diurnal tide, a pi'oblem not hitherto solved by ob- ' 

 servation ; and the second class of observations being intended 

 to illustrate the laws of the semidiurnal tide, pai'ticularly in the 

 Irish Channel, and to decide the true mean height of the water 

 round the coasts of Ireland. 



In the present communication, I shall give the results of the 

 calculations made from the daily observations, with a view to 

 determine the separate effects of the sun and moon upon the 

 diurnal tide. 



Section I. Description of the Tidal Stations and of the Tide- 

 gauge used in the observations. 



I. Castletowusend, Co. Cork. 

 Lat. 51° 31' N. Long. 9° 7' W. 



The zero of the tide-gauge was carefully referred to the iron 

 bolt driven vertically into the rock in which the Coast-guard 

 signal-staff is secured. 



The zero was 31-91 feet below this bolt. The gauge at this 

 station was placed in the open sea, and was held in its place by 

 stays and guys made fast to the rock. 



