Shown by Recording Tide-gauges. 



127 



motions of different periods, the irregularity is at times mark- 

 edly regular, showing the coexistence of at least two systems 

 of undulations. As will be seen by H^. 2, the undulations at 



Hours. 



Figure 2. — Types of secondary undulations at Halifax, N. S. 



times become simple and quite remarkably regular. At such 

 times the period is either about 20 minutes or about 33 minutes. 

 The figure shows both series and the apparent composition of 

 the two in the third curve. 



I pass now to a consideration of the records from stations 

 on the Gulf of St. Lawrence and adjacent basins. 



1. St. Paul's Island (in Cabot Strait between Newfoundland 

 and Cape Breton, X. S. and connecting the Gulf of St. Law- 

 rence with the Atlantic Ocean). The secondary undulations 

 are here practically continuous and vary from fine shadings so 



