TRANSACTIONS OF THE SECTIONS. 5 



particular the channel became very narrow between Donaghadee and Portpatrick, 

 and indeed the entire Scotch coast to the Mull of Kintyre, and the island of Hay. 

 Stations were carefully selected on all these different seas. Besides this, stations 

 were selected at different points of some of the estuaries, for investigation of the 

 change in the nature of the tide as it proceeds up the estuaries : thus four stations 

 were selected on the estuary of the Shannon. He did not then particularize all 

 the motives which swayed them, but stated generally that twenty-two stations round 

 the coast were fixed upon. On the 22nd of June 1842, they had all their observers 

 at the several stations, and the observations were continued for full two months, viz. 

 until the 26th of August. He need scarcely say, that there were four critical phse- 

 nomenaor periods, in each twenty-four hours, to be noted carefully, viz. the instants 

 of each of the two high waters, and the instants of each of the intervening low 

 waters, and although the season was chosen so that the nights should be short, yet 

 one at least of these four critical phsenomena must occur in the night : as it would 

 therefore be too laborious to record at sufficiently close intervals during the entire 

 twenty-four hours, the orders given to the observers were to be at their posts at least 

 half an hour before by any possibility each of these four states of the tide could 

 occur, and then to record every five minutes the actual height. In the night, the 

 registrations were continued only till the tide had taken a decided turn ; but in the 

 day, the observations were continued incessantly from the time of beginning before 

 the first critical phsenomenon till the tide had taken a decided turn after the third 

 critical phaenomenon. At some of the stations, however, the observations were made 

 continuously during the twenty-four hours ; to one of them, Courtown, he should have 

 to direct particular attention. The researches of Professor Whewell and of Sir John 

 Lubbock had rendered a close attention to the diurnal and semi-diurnal inequalities 

 of the tides a matter of interest. One of the earliest and most immediate results of 

 these systematized observations was, that the high tide was found to be simultaneous 

 along the entire western and south-western coasts, apparently coming from the west. 

 It was also simultaneous along the eastern coast, but strange to say, with a jump of 

 no less than six hours between these two clearly defined times of high water : so 

 that they were met in the first stage of their speculations by the fact, that there was 

 a difference of no less than six hours between the time of high water at Dunmore 

 (mouth of the Waterford harbour) and at Dublin. This was for a time a puzzle ; but 

 from it might be inferred what they afterwards found verified by the observations at 

 Courtown, that a node, or place of no tide, must occur at some intervening place. 

 Another result was, that the diurnal tide came apparently not from the west, but 

 from the south-west. The observations have been grouped and discussed by the new 

 mode pointed out by him in the Philosophical Transactions for 1842, in which the 

 heights were expressed as a function of the times by the following formula : 



L=A-|-B . sin^-l-C . sin (2^-f-c)-l-D . sin (3^+d)-f &c. 

 By this method, about 1400 individual tides, observed at all the stations, had been 

 discussed. From this discussion, it appeared that the great tide wave was two days 

 old when it reached Ireland, and that the solar effect exerted in raising the water was 

 about one-third of that of the moon, if the deductions were made from the tides of 

 the more open western and south-western parts of the coast ; while the inferences 

 deduced from those of the north-eastern coast, would make it in some places only 

 one-sixth, and in other places about one-half. At some of the stations of the north- 

 eastern coast, an enormous amount of semi-diurnal inequality manifested itself: 

 the semi-menstrual inequality was also found to be considerable there. Another 

 remarkable and unexpected irregularity also resulted from these discussions ; which 

 was a difference of no less than one foot between the mean heights of the tides of the 

 western and southern, and the north-eastern coasts ; the mean heights of the tides, 

 or values of A, in the preceding formula, being one foot greater for the north-eastern 

 than for the south-western stations. It was also found that the irregularities in the 

 values of A, from day to day, agreed very closely on a long line of coast : and this 

 fact afforded the most demonstrative proof of the accuracy of the observers, for while 

 it manifested itself most distinctly at each of the stations in going round the coast, 

 its amount and its variations were so consistent, as to render it absolutely impossible 

 that it could have resulted from careless observations. He then directed attention 

 to the Courtown station, stating that at the commencement of their labours here the 



