S8 ROYAL SOCIETY OF CANADA 



Miramichi, and returns along the north coast of Prince Edward Island to 

 its extreme eastern end. In passing the western end of Northumberland 

 strait, there is interference between this tide and the direct tide which 

 enters the strait by its eastern end. The result of this is, that in the 

 western end of Northumberland strait, from Shediac to Richibucto, the 

 tide is almost effaced ; and the time of the tide is difficult, if not impos- 

 sible, to determine with any certainty. 



There appears to be an extensive interference in the open Gulf alsO) 

 between this undulation, which returns from the region of Miramichi bay 

 along the north coast of Prince Edward Island eastwards, and the follow- 

 ing tide Avhich enters through Cabot strait. Thus we find the tide to be 

 nearly simultaneous along the north shore of Prince Edward Island, 

 which points to the meeting of two undulations from opposite directions, 

 rather than to interference from the Belle Isle tide ; as this would run 

 across the main tide at right angles and would affect its ran<je, but would 

 not alter appreciably the time of the tide. It may possibly be this return 

 undulation which gives rise to the inequalities observed at St. Paul island 

 itself. This would also show why the tide in the St. Lawrence estuary is 

 free fi-om these irregularities; because the tide from the Atlantic, although 

 overrun by this return undulation while passing thi'ough the G-ulf, is 

 again free from it on entering the mouth of the St. Lawrence ; as this is 

 beyond the point at which the return undulation begins. This would be 

 in accordance with the usual laws of the interference of undulatory 

 movements. 



This explanation of the nature of the tidal interference in the Gulf is 

 further corroborated by the investigation of the difference in the time of 

 the tide at points along the open shore of the Gulf, to which we are now 

 referring. These differences, if taken for the same tide followed on its 

 course from Cabot strait, are so irregular as to be entirely valueless. 

 This, therefore, shows the interference to be of the nature of a return 

 undulation ; as it reverses the diurnal inequality in the tide at the two 

 sides of the Gulf with respect to each other. (Compare the tides at St. 

 Paul island and Carleton, as given in Plates III. and IV., and in Plate 



We find accordingly, that on these coasts the only tidal differences 

 which approach to constancy, are those between high water at any point, 

 and the next following high water at St. Paul island. A number of com- 

 parisons were made in the endeavour to refer these tides l)y constant dif- 

 ference to some other Gulf station, such as Pictou, or Southwest Point, 

 Anticosti ; but St. Paul island itself was found to be the only station to 

 which they could be referred with any reasonable degree of accuracy. 



