Shown by Recording Tide-gauges. 129 



6. Cape Tormentine, !N~. B. (on the narrowest part of North- 

 umberland Strait). Apparently no secondary undulations. 



7. Lower Neguac, N. B. (at mouth of Miramichi Bay, where 

 the gauge was placed "to obtain the open tide unaffected by 

 the bars and rivers of the bay "). No evidence at all of sec- 

 ondary undulations. 



8. Carleton, Quebec (on Chaleur Bay, a branch of the Gulf). 

 Secondary undulations occur about once a week, but of such 

 small extent and duration that no period can be deduced. 



9. South West Point, Anticosti. Secondary undulations 

 are almost incessant and frequently very irregular, but at 

 times clear, regular, well sustained undulations occur :* 18, 18, 

 18, 19, 20, 18, 18, 18, 21, 20, 21— mean 19 m. 



10. Grindstone Island (of the Magdalen Island group in the 

 middle of the Gulf). Secondary undulations are nearly inces- 

 sant but quite irregular and no clear period is found. (The 

 data are perhaps insufficient as the gauge was only a short time 

 in action.) 



11. Forteau Bay (on the Strait of Belle Isle, between New- 

 foundland and Labrador). Secondary undulations are almost 

 incessant, and usually very irregular. Rarely does a clear 

 period emergef : IT, 15, 16 — mean 16m. 



Resume,. 



The secondary undulations at any place are at times irregular 

 (rarely at St. John), at other times regular (perhaps never at 

 Grindstone Island) ; when they are regular the period of 

 oscillation has a distinct and characteristic value for each place, 

 varying from place to place, from less than a minute to over 

 an hour. The amplitude also varies widely. At some places 

 at least two systems of regular oscillations of different periods 

 are found ; these may exist together (Halifax), or the period 

 at low tide may be distinct from the period at high tide (Yar- 

 mouth). 



Theories advanced to explain Secondary Undulations. 



It will be convenient at this point to summarize the theories 

 that have been offered to account for the preceding phenomena. 

 There are two chief points that require explanation, the ori- 

 gin of the initial disturbance and the particular period (or 

 periods) at each place. These two points may be entirely dis- 

 tinct or the explanation of one may include that of the other. 



* Because of some slight difficulty in ascertaining exact dates I noted number 

 of tidal sheet:— 238 (7), 238 (12), 241 (8), 249 (5). 249 (5), 256 (25), 261 (8), 262 

 (9), 271 (5), 271 (5). 274 (5). 



f These all occurred on Oct 30-31, 1898. 



