Shown by Recording Tide-gauges. 131 



surface of the sea, tend to form minute undulations upon the 

 surface, corresponding to the length of the billows, which, as 

 they move farther into the bay, become magnified as they 

 reach narrower and shallower portions." In a later paper Mr. 

 Denison repeats the above views and states that " there is a 

 marked relative correspondence in amplitude between the 

 barometric and water undulations," adding many interesting 

 speculations concerning a possible connection between second- 

 ary undulations and warm and cold waves, precipitation, etc., 

 but we are not concerned with them at present. (It may be 

 added that Mr. Denison's papers are very brief, containing but 

 six pages in all and, excepting one case of secondary undula- 

 tion at Halifax, giving no references in detail to the coinci- 

 dences of barometric, meteorological and tidal records on 

 which the theory is founded, so that, in again traversing the 

 same ground, I was unable to refer directly to the evidence for 

 the deductions.) 



The above is primarily a theory of the origin of the dis- 

 turbances. It would at first sight not seem incompatible with 

 any other explanation of the period. 



These theories will be tested in the sections that follow. 



Comparison of observed and calculated periods. 



In order to test how far the seiche theory, advanced for the 

 cases at St. John, would apply in general, I calculated from 

 the admiralty charts the width and mean depth of basins and 

 channels immediately adjacent to several of the above men- 

 tioned stations and therefrom deduced the period in which such 

 bodies of water should vibrate. 



Station. 

 St. John Harbor 

 St. John River 

 Westport 

 Yarmouth 

 Souris 



Farther Point 

 S.W. Point 

 Fortcau Bay 



The above calculated periods can only be considered as 

 roughly approximate. They suffice, however, to show that, 

 except in the first four cases, the periods cannot be those of 

 binodal seiches, and if they are seiche periods at all the 

 seiches must be multinodal (e. g., at S.W. Pt. and Forteau 

 Bay trinodal, at Farther Pt. quinque nodal). Local peculiari- 

 ties, for example variation in the depth of the basin, would, 







Period calculated. 



Basin or Channel. 



Period observed. 



binodal. 



uninodal. 



Bay of Fundy 



41 m. 



43*5 



m. 



81 m 



(small bay) 



35 sec. 



37*5 



s. 



12 s. 



St. Margaret's Bay 



16 m. 



14 



m. 



28 m, 



N.S. to Lurcher Shoal 



30 m., 69 m. 



30 



m. 



60 m, 



Northumberland Strait 



21 m. 



45 



m. 



90 m 



St. Lawrence River 



21 m. 



50 



m. 



100 m 



Anticosti to Gaspe 



19 m. 



30 



m. 



60 m, 



Strait of Belle Isle 



16 m. 



23 



m. 



41 m, 



